eperl - Online in the Cloud

PROGRAM:

NAME

ePerl - Embedded Perl 5 Language

VERSION

@V@

SYNOPSIS

eperl [-d name=value] [-D name=value] [-B begin_delimiter] [-E end_delimiter] [-i] [-m
mode] [-o outputfile] [-k] [-I directory] [-P] [-C] [-L] [-x] [-T] [-w] [-c] [inputfile]

eperl [-r] [-l] [-v] [-V]

DESCRIPTION

Abstract
ePerl interprets an ASCII file bristled with Perl 5 program statements by evaluating the
Perl 5 code while passing through the plain ASCII data. It can operate in various ways: As
a stand-alone Unix filter or integrated Perl 5 module for general file generation tasks
and as a powerful Webserver scripting language for dynamic HTML page programming.

Introduction
The eperl program is the Embedded Perl 5 Language interpreter. This really is a full-
featured Perl 5 interpreter, but with a different calling environment and source file
layout than the default Perl interpreter (usually the executable perl or perl5 on most
systems). It is designed for general ASCII file generation with the philosophy of
embedding the Perl 5 program code into the ASCII data instead of the usual way where you
embed the ASCII data into a Perl 5 program (usually by quoting the data and using them via
"print" statements). So, instead of writing a plain Perl script like

#!/path/to/perl
print "foo bar\n";
print "baz quux\n";
for ($i = 0; $i < 10; $i++) { print "foo #${i}\n"; }
print "foo bar\n";
print "baz quux\n";

you can write it now as an ePerl script:

#!/path/to/eperl
foo bar
baz quux
<: for ($i = 0; $i < 10; $i++) { print "foo #${i}\n"; } :>
foo bar
baz quux

Although the ePerl variant has a different source file layout, the semantic is the same,
i.e. both scripts create exactly the same resulting data on "STDOUT".

Intention
ePerl is simply a glue code which combines the programming power of the Perl 5 interpreter
library with a tricky embedding technique. The embedding trick is this: it converts the
source file into a valid Perl script which then gets entirely evaluated by only one
internal instance of the Perl 5 interpreter. To achieve this, ePerl translates all plain
code into (escaped) Perl 5 strings placed into print constructs while passing through all
embedded native Perl 5 code. As you can see, ePerl itself does exactly the same
internally, a silly programmer had to do when writing a plain Perl generation script.

Due to the nature of such bristled code, ePerl is really the better attempt when the
generated ASCII data contains really more static as dynamic data. Or in other words: Use
ePerl if you want to keep the most of the generated ASCII data in plain format while just
programming some bristled stuff. Do not use it when generating pure dynamic data. There it
brings no advantage to the ordinary program code of a plain Perl script. So, the static
part should be at least 60% or the advantage becomes a disadvantage.

ePerl in its origin was actually designed for an extreme situation: as a webserver
scripting-language for on-the-fly HTML page generation. Here you have the typical case
that usually 90% of the data consists of pure static HTML tags and plain ASCII while just
the remaining 10% are programming constructs which dynamically generate more markup code.
This is the reason why ePerl beside its standard Unix filtering runtime-mode also supports
the CGI/1.1 and NPH-CGI/1.1 interfaces.

Embedded Perl Syntax
Practically you can put any valid Perl constructs inside the ePerl blocks the used Perl 5
interpreter library can evaluate. But there are some important points you should always
remember and never forget when using ePerl:

1. Delimiters are always discarded.
Trivially to say, but should be mentioned at least once. The ePerl block delimiters
are always discarded and are only necessary for ePerl to recognize the embedded Perl
constructs. They are never passed to the final output.

2. Generated content has to go to "STDOUT".
Although you can define subroutines, calculate some data, etc. inside ePerl blocks
only data which is explicitly written to the "STDOUT" filehandle is expanded. In other
words: When an ePerl block does not generate content on "STDOUT", it is entirely
replaced by an empty string in the final output. But when content is generated it is
put at the point of the ePerl block in the final output. Usually contents is generated
via pure "print" constructs which implicitly use "STDOUT" when no filehandle is given.

3. Generated content on "STDERR" always leads to an error.
Whenever content is generated on the "STDERR" filehandle, ePerl displays an error
(including the STDERR content). Use this to exit on errors while passing errors from
ePerl blocks to the calling environment.

4. Last semicolon.
Because of the following point 6 (see below) and the fact that most of the users don't
have the internal ePerl block translations in mind, ePerl is smart about the last
semicolon. Usually every ePerl block has to end with the semicolon of the last
command.

<: cmd; ...; cmd; :>

But when the last semicolon is missing it is automatically added by ePerl, i.e.

<: cmd; ...; cmd :>

is also correct syntax. But sometimes it is necessary to force ePerl not to add the
semicolon. Then you can add a ``"_"'' (underscore) as the last non-whitespace
character in the block to force ePerl to leave the final semicolon. Use this for
constructs like the following

<: if (...) { _:>
foo
<: } else { _:>
bar
<: } :>

where you want to spread a Perl directive over more ePerl blocks.

5. Shorthand for "print"-only blocks.
Because most of the time ePerl is used just to interpolate variables, e.g.

<: print $VARIABLE; :>

it is useful to provide a shortcut for this kind of constructs. So ePerl provides a
shortcut via the character '='. When it immediately (no whitespaces allowed here)
follows the begin delimiter of an ePerl block a "print" statement is implicitly
generated, i.e. the above block is equivalent to

<:=$VARIABLE:>

Notice that the semicolon was also removed here, because it gets automatically added
(see above).

6. Special EndOfLine discard command for ePerl blocks.
ePerl provides a special discard command named ``"//"'' which discards all data up-to
and including the following newline character when directly followed an end block
delimiter. Usually when you write

foo
<: $x = 1; :>
quux

the result is

foo

quux

because ePerl always preserves code around ePerl blocks, even just newlines. But when
you write

foo
<: $x = 1; :>//
quux

the result is

foo
quux

because the ``"//"'' deleted all stuff to the end of the line, including the newline.

7. Restrictions in parsing.
Every program has its restrictions, ePerl too. Its handicap is that Perl is not only a
rich language, it is a horrible one according to parsing its constructs. Perhaps you
know the phrase ,,Only perl can parse Perl''. Think about it. The implication of this
is that ePerl never tries to parse the ePerl blocks itself. It entirely relies on the
Perl interpreter library, because it is the only instance which can do this without
errors. But the problem is that ePerl at least has to recognize the begin and end
positions of those ePerl blocks.

There are two ways: It can either look for the end delimiter while parsing but at
least recognize quoted strings (where the end delimiter gets treated as pure data). Or
it can just move forward to the next end delimiter and say that it have not occur
inside Perl constructs. In ePerl 2.0 the second one was used, while in ePerl 2.1 the
first one was taken because a lot of users wanted it this way while using bad end
delimiters like ``">"''. But actually the author has again revised its opinion and
decided to finally use the second approach which is used since ePerl 2.2 now. Because
while the first one allows more trivial delimiters (which itself is not a really good
idea), it fails when constructs like ``"m|"[^"]+"|"'' etc. are used inside ePerl
blocks. And it is easier to escape end delimiters inside Perl constructs (for instance
via backslashes in quoted strings) than rewrite complex Perl constructs to use even
number of quotes.

So, whenever your end delimiter also occurs inside Perl constructs you have to escape
it in any way.

8. HTML entity conversion.
Because one of ePerl's usage is as a server-side scripting-language for HTML pages,
there is a common problem in conjunction with HTML editors. They cannot know ePerl
blocks, so when you enter those blocks inside the editors they usually encode some
characters with the corresponding HTML entities. The problem is that this encoding
leads to invalid Perl code. ePerl provides the option -C for decoding these entities
which is automatically turned on in CGI modes. See description below under option -C
for more details.

Runtime Modes
ePerl can operate in three different runtime modes:

Stand-alone Unix filter mode
This is the default operation mode when used as a generation tool from the Unix shell
or as a batch-processing tool from within other programs or scripts:

$ eperl [options] - < inputfile > outputfile
$ eperl [options] inputfile > outputfile
$ eperl [options] -o outputfile - < inputfile
$ eperl [options] -o outputfile inputfile

As you can see, ePerl can be used in any combination of STDIO and external files.
Additionally there are two interesting variants of using this mode. First you can use
ePerl in conjunction with the Unix Shebang magic technique to implicitly select it as
the interpreter for your script similar to the way you are used to with the plain Perl
interpreter:

#!/path/to/eperl [options]
foo
<: print "bar"; :>
quux

Second, you can use ePerl in conjunction with the Bourne-Shell Here Document technique
from within you shell scripts:

#!/bin/sh
...
eperl [options] - <<EOS
foo
<: print "quux"; :>
quux
EOS
...

If you need to generate shell or other scripts with ePerl, i.e. you need a shebang
line in the output of eperl, you have to add a shebang line containing e.g.
"#!/usr/bin/eperl" first, because eperl will strip the first line from the input if it
is a shebang line. Example:

#!/usr/bin/eperl
#!/bin/sh
echo <: print "quux"; :>

will result in the following output:

#!/bin/sh
echo quux

Alternatively you can add a preprocessor comment in the first line, e.g. like this:

#c This is a comment to preserve the shebang line in the following line
#!/bin/sh
echo <: print "quux"; :>

And finally you can use ePerl directly from within Perl programs by the use of the
Parse::ePerl(3) package (assuming that you have installed this also; see file INSTALL
inside the ePerl distribution for more details):

#!/path/to/perl
...
use Parse::ePerl;
...
$script = <<EOT;
foo
<: print "quux"; :>
quux
EOT
...
$result = Parse::ePerl::Expand({
Script => $script,
Result => \$result,
});
...
print $result;
...

See Parse::ePerl(3) for more details.

CGI/1.1 compliant interface mode
This is the runtime mode where ePerl uses the CGI/1.1 interface of a webserver when
used as a Server-Side Scripting Language on the Web. ePerl enters this mode
automatically when the CGI/1.1 environment variable "PATH_TRANSLATED" is set and its
or the scripts filename does not begin with the NPH prefix ``nph-''. In this runtime
mode it prefixes the resulting data with HTTP/1.0 (default) or HTTP/1.1 (if identified
by the webserver) compliant response header lines.

ePerl also recognizes HTTP header lines at the beginning of the scripts generated
data, i.e. for instance you can generate your own HTTP headers like

<? $url = "..";
print "Location: $url\n";
print "URI: $url\n\n"; !>
<html>
...

But notice that while you can output arbitrary headers, most webservers restrict the
headers which are accepted via the CGI/1.1 interface. Usually you can provide only a
few specific HTTP headers like "Location" or "Status". If you need more control you
have to use the NPH-CGI/1.1 interface mode.

Additionally ePerl provides a useful feature in this mode: It can switch its UID/GID
to the owner of the script if it runs as a Unix SetUID program (see below under
Security and the option ``u+s'' of chmod(1)).

There are two commonly known ways of using this CGI/1.1 interface mode on the Web.
First, you can use it to explicitly transform plain HTML files into CGI/1.1 scripts
via the Shebang technique (see above). For an Apache webserver just put the following
line as the first line of the file:

#!/path/to/eperl -mc

Then rename the script from file.html to file.cgi and set its execution bit via

$ mv file.html file.cgi
$ chmod a+rx file.cgi

Now make sure that Apache accepts file.cgi as a CGI program by enabling CGI support
for the directory where file.cgi resides. For this add the line

Options +ExecCGI

to the .htaccess file in this directory. Finally make sure that Apache really
recognizes the extension .cgi. Perhaps you additionally have to add the following line
to your httpd.conf file:

AddHandler cgi-script .cgi

Now you can use file.cgi instead of file.html and make advantage of the achieved
programming capability by bristling file.cgi with your Perl blocks (or the
transformation into a CGI script would be useless).

Alternatively (or even additionally) a webmaster can enable ePerl support in a more
seamless way by configuring ePerl as a real implicit server-side scripting language.
This is done by assigning a MIME-type to the various valid ePerl file extensions and
forcing all files with this MIME-type to be internally processed via the ePerl
interpreter. You can accomplish this for Apache by adding the following to your
httpd.conf file

AddType application/x-httpd-eperl .phtml .eperl .epl
Action application/x-httpd-eperl /internal/cgi/eperl
ScriptAlias /internal/cgi /path/to/apache/cgi-bin

and creating a copy of the eperl program in your CGI-directory:

$ cp -p /path/to/eperl /path/to/apache/cgi-bin/eperl

Now all files with the extensions .phtml, .eperl and .epl are automatically processed
by the ePerl interpreter. There is no need for a Shebang line or any locally enabled
CGI mode.

One final hint: When you want to test your scripts offline, just run them with forced
CGI/1.1 mode from your shell. But make sure you prepare all environment variables your
script depends on, e.g. "QUERY_STRING" or "PATH_INFO".

$ export QUERY_STRING="key1=value1&key2=value2"
$ eperl -mc file.phtml

NPH-CGI/1.1 compliant interface mode
This runtime mode is a special variant of the CGI/1.1 interface mode, because most
webservers (e.g. Apache) provide it for special purposes. It is known as Non-Parsed-
Header (NPH) CGI/1.1 mode and is usually used by the webserver when the filename of
the CGI program is prefixed with ``"nph-"''. In this mode the webserver does no
processing on the HTTP response headers and no buffering of the resulting data, i.e.
the CGI program actually has to provide a complete HTTP response itself. The advantage
is that the program can generate arbitrary HTTP headers or MIME-encoded multi-block
messages.

So, above we have renamed the file to file.cgi which restricted us a little bit. When
we alternatively rename file.html to nph-file.cgi and force the NPH-CGI/1.1 interface
mode via option -mn then this file becomes a NPH-CGI/1.1 compliant program under
Apache and other webservers. Now our script can provide its own HTTP response (it need
not, because when absent ePerl provides a default one for it).

#!/path/to/bin/eperl -mn
<? print "HTTP/1.0 200 Ok\n";
print "X-MyHeader: Foo Bar Quux\n";
print "Content-type: text/html\n\n";
<html>
...

As you expect this can be also used with the implicit Server-Side Scripting Language
technique. Put

AddType application/x-httpd-eperl .phtml .eperl .epl
Action application/x-httpd-eperl /internal/cgi/nph-eperl
ScriptAlias /internal/cgi /path/to/apache/cgi-bin

into your httpd.conf and run the command

$ cp -p /path/to/eperl /path/to/apache/cgi-bin/nph-eperl

from your shell. This is the preferred way of using ePerl as a Server-Side Scripting
Language, because it provides most flexibility.

Security
When you are installing ePerl as a CGI/1.1 or NPH-CGI/1.1 compliant program (see above for
detailed description of these modes) via

$ cp -p /path/to/eperl /path/to/apache/cgi-bin/eperl
$ chown root /path/to/apache/cgi-bin/eperl
$ chmod u+s /path/to/apache/cgi-bin/eperl

or

$ cp -p /path/to/eperl /path/to/apache/cgi-bin/nph-eperl
$ chown root /path/to/apache/cgi-bin/nph-eperl
$ chmod u+s /path/to/apache/cgi-bin/nph-eperl

i.e. with SetUID bit enabled for the root user, ePerl can switch to the UID/GID of the
scripts owner. Although this is a very useful feature for script programmers (because one
no longer need to make auxiliary files world-readable and temporary files world-
writable!), it can be to risky for you when you are paranoid about security of SetUID
programs. If so just don't install ePerl with enabled SetUID bit! This is the reason why
ePerl is per default only installed as a Stand-Alone Unix filter which never needs this
feature.

For those of us who decided that this feature is essential for them ePerl tries really
hard to make it secure. The following steps have to be successfully passed before ePerl
actually switches its UID/GID (in this order):

1. The script has to match the following extensions:
.html, .phtml, .ephtml, .epl, .pl, .cgi
2. The UID of the calling process has to be a valid UID,
i.e. it has to be found in the systems password file
3. The UID of the calling process has to match the
following users: root, nobody
4. The UID of the script owner has to be a valid UID,
i.e. it has to be found in the systems password file
5. The GID of the script group has to be a valid GID,
i.e. it has to be found in the systems group file
6. The script has to stay below or in the owners homedir

IF ONLY ONE OF THOSE STEPS FAIL, NO UID/GID SWITCHING TAKES PLACE!. Additionally (if
"DO_ON_FAILED_STEP" was defined as "STOP_AND_ERROR" in eperl_security.h - not per default
defined this way!) ePerl can totally stop processing and display its error page. This is
for the really paranoid webmasters. Per default when any step failed the UID/GID switching
is just disabled, but ePerl goes on with processing. Alternatively you can disable some
steps at compile time. See eperl_security.h.

Also remember that ePerl always eliminates the effective UID/GID, independent of the
runtime mode and independent if ePerl has switched to the UID/GID of the owner. For
security reasons, the effective UID/GID is always destroyed before the script is executed.

ePerl Preprocessor
ePerl provides an own preprocessor similar to CPP in style which is either enabled
manually via option -P or automatically when ePerl runs in (NPH-)CGI mode. The following
directives are supported:

"#include path"
This directive is an include directive which can be used to include really any stuff,
but was actually designed to be used to include other ePerl source files. The path can
be either a relative or absolute path for the local filesystem or a fully qualified
HTTP URL.

In case of the absolute path the file is directly accessed on the filesystem, while
the relative path is first searched in the current working directory and then in all
directories specified via option -I. In the third case (HTTP URL) the file is
retrieves via a HTTP/1.0 request on the network. Here HTTP redirects (response codes
301 and 302) are supported, too.

Notice: While ePerl strictly preserves the line numbers when translating the bristled
ePerl format to plain Perl format, the ePerl preprocessor can't do this (because its a
preprocessor which expands) for this directive. So, whenever you use "#include",
remember that line numbers in error messages are wrong.

Also notice one important security aspect: Because you can include any stuff as it is
provided with this directive, use it only for stuff which is under your direct
control. Don't use this directive to include foreign data, at least not from external
webservers. For instance say you have a ePerl page with "#include
http://www.foreigner.com/nice-page.html" and at the next request of this page your
filesystem is lost! Why? Because the foreigner recognizes that you include his page
and are using ePerl and just put a simple ``"<? system("rm -rf /"); !>"'' in his
page. Think about it. NEVER USE #INCLUDE FOR ANY DATA WHICH IS NOT UNDER YOUR OWN
CONTROL. Instead always use "#sinclude" for such situations.

"#sinclude path"
This is the secure variant of "#include" where after reading the data from path all
ePerl begin and end delimiters are removed. So risky ePerl blocks lost their meaning
and are converted to plain text. Always use this directive when you want to include
data which is not under your own control.

"#if expr", "#elsif expr", "#else", "#endif"
These implement a CPP-style "#if-[#else-]#endif" construct, but with a Perl semantic.
While the other directives are real preprocessor commands which are evaluated at the
preprocessing step, this construct is actually just transformed into a low-level ePerl
construct, so it is not actually evaluated at the preprocessing step. It is just a
handy shortcut for the following (where BD is the currently used begin delimiter and
ED the end delimiter):

``#if expr'' -> ``BD if (expr) { _ ED//''
``#elsif expr'' -> ``BD } elsif (expr) { _ ED//''
``#else'' -> ``BD } else { _ ED//''
``#endif'' -> ``BD } _ ED//''

The advantage of this unusual aproach is that the if-condition really can be any valid
Perl expression which provides maximum flexibility. The disadvantage is that you
cannot use the if-construct to make real preprocessing decisions. As you can see, the
design goal was just to provide a shorthand for the more complicated Perl constructs.

"#c"
This is the comment directive which just discards all data up to and including the
newline character. Use this one to comment out any stuff, even other preprocessor
directives.

Provided Functionality
Up to know you've understand that ePerl provides a nice facility to embed Perl code into
any ASCII data. But now the typical question is: Which Perl code can be put into these
ePerl blocks and does ePerl provide any special functionality inside these ePerl blocks?

The answers are: First, you can put really any Perl code into the ePerl blocks which are
valid to the Perl interpreter ePerl was linked with. Second, ePerl does not provide any
special functionality inside these ePerl blocks, because Perl is already sophisticated
enough ;-)

The implication of this is: Because you can use any valid Perl code you can make use of
all available Perl 5 modules, even those ones which use shared objects (because ePerl is a
Perl interpreter, including DynaLoader support). So, browse to the Comprehensive Perl
Archive Network (CPAN) via http://www.perl.com/perl/CPAN and grab your favorite packages
which can make your life easier (both from within plain Perl scripts and ePerl scripts)
and just use the construct ``"use name;"'' in any ePerl block to use them from within
ePerl.

When using ePerl as a Server-Side-Scripting-Language I really recommend you to install at
least the packages CGI.pm (currently vers. 2.36), HTML-Stream (1.40), libnet (1.0505) and
libwww-perl (5.08). When you want to generate on-the-fly images as well, I recommend you
to additionally install at least GD (1.14) and Image-Size (2.3). The ePerl interpreter in
conjunction with these really sophisticated Perl 5 modules will provide you with maximum
flexibility and functionality. In other words: Make use of maximum Software Leverage in
the hackers world of Perl as great as possible.

OPTIONS

-d name=value
Sets a Perl variable in the package "main" which can be referenced via $name or more
explicitly via $main::name. The command

eperl -d name=value ..

is actually equivalent to having

<? $name = value; !>

at the beginning of inputfile. This option can occur more than once.

-D name=value
Sets a environment variable which can be referenced via $ENV{'variable'} inside the
Perl blocks. The command

eperl -D name=value ..

is actually equivalent to

export name=value; eperl ...

but the advantage of this option is that it doesn't manipulate the callers
environment. This option can occur more than once.

-B begin_delimiter
Sets the Perl block begin delimiter string. Use this in conjunction with "-E" to set
different delimiters when using ePerl as an offline HTML creation-language while still
using it as an online HTML scripting-language. Default delimiters are "<?" and "!>"
for CGI modes and "<:" and ":>" for stand-alone Unix filtering mode.

There are a lot of possible variations you could choose: ""<:"" and "":>"" (the
default ePerl stand-alone filtering mode delimiters), ""<?"" and ""!>"" (the default
ePerl CGI interface mode delimiters), ""<script language='ePerl'>"" and ""</script>""
(standard HTML scripting language style), ""<script type="text/eperl">"" and
""</script>"" (forthcoming HTML3.2+ aka Cougar style), ""<eperl>"" and ""</eperl>""
(HTML-like style), ""<!--#eperl code='"" and ""' -->"" (NeoScript and SSI style) or
even ""<?"" and "">"" (PHP/FI style; but this no longer recommended because it can
lead to parsing problems. Should be used only for backward compatibility to old ePerl
versions 1.x).

The begin and end delimiters are searched case-insensitive.

-E end_delimiter
Sets the Perl block end delimiter string. See also option -B.

-i Forces the begin and end delimiters to be searched case-insensitive. Use this when
you are using delimiters like ``"<ePerl>"..."</ePerl>"'' or other more textual ones.

-m mode
This forces ePerl to act in a specific runtime mode. See above for a detailed
description of the three possible modes: Stand-alone filter (mode="f", i.e. option
-mf), CGI/1.1 interface mode (mode="c", i.e. option -mc) or the NPH-CGI/1.1 interface
mode (mode="n", i.e. option -mn).

-o outputfile
Forces the output to be written to outputfile instead of STDOUT. Use this option when
using ePerl as a filter. The outputfile ``-'' sets STDOUT as the output handle
explicitly. Notice that this file is relative to the source file directory when the
runtime mode is forced to CGI or NPH-CGI.

-k Forces ePerl to keep the current working directory from where it was started. Per
default ePerl will change to the directory where the file to be executed stays. This
option is useful if you use ePerl as an offline filter on a temporary file.

-x This sets debug mode where ePerl outputs the internally created Perl script to the
console (/dev/tty) before executing it. Only for debugging problems with the inputfile
conversion.

-I directory
Specify a directory which is both used for "#include" and "#sinclude" directives of
the ePerl preprocessor and added to @INC under runtime. This option can occur more
than once.

-P Manually enables the special ePerl Preprocessor (see above). This option is enabled
for all CGI modes automatically.

-C This enables the HTML entity conversion for ePerl blocks. This option is automatically
forced in CGI modes.

The solved problem here is the following: When you use ePerl as a Server-Side-
Scripting-Language for HTML pages and you edit your ePerl source files via a HTML
editor, the chance is high that your editor translates some entered characters to HTML
entities, for instance ``"<"'' to ``"&lt;"''. This leads to invalid Perl code inside
ePerl blocks, because the HTML editor has no knowledge about ePerl blocks. Using this
option the ePerl parser automatically converts all entities found inside ePerl blocks
back to plain characters, so the Perl interpreter again receives valid code blocks.

-L This enables the line continuation character ``"\"'' (backslash) outside ePerl blocks.
With this option you can spread oneline-data over more lines. But use with care: This
option changes your data (outside ePerl blocks). Usually ePerl really pass through
all surrounding data as raw data. With this option the newlines become new semantics.

-T This enabled Perl's Tainting mode where the Perl interpreter takes special precautions
called taint checks to prevent both obvious and subtle traps. See perlsec(1) for more
details.

-w This enables Warnings where the Perl interpreter produces some lovely diagnostics. See
perldiag(1) for more details.

-c This runs a pure syntax check which is similar to ``"perl -c"''.

-r This prints the internal ePerl README file to the console.

-l This prints the internal ePerl LICENSE file to the console.

-v This prints ePerl version information to the console.

-V Same as option -v but additionally shows the Perl compilation parameters.

ENVIRONMENT

Used Variables
"PATH_TRANSLATED"
This CGI/1.1 variable is used to determine the source file when ePerl operates as a
NPH-CGI/1.1 program under the environment of a webserver.

Provided Variables
"SCRIPT_SRC_PATH"
The absolute pathname of the script. Use this when you want to directly access the
script from within itself, for instance to do "stat()" and other calls.

"SCRIPT_SRC_PATH_DIR"
The directory part of "SCRIPT_SRC_PATH". Use this one when you want to directly access
other files residing in the same directory as the script, for instance to read config
files, etc.

"SCRIPT_SRC_PATH_FILE"
The filename part of "SCRIPT_SRC_PATH". Use this one when you need the name of the
script, for instance for relative self-references through URLs.

"SCRIPT_SRC_URL"
The fully-qualified URL of the script. Use this when you need a URL for self-
reference.

"SCRIPT_SRC_URL_DIR"
The directory part of "SCRIPT_SRC_URL". Use this one when you want to directly access
other files residing in the same directory as the script via the Web, for instance to
reference images, etc.

"SCRIPT_SRC_URL_FILE"
The filename part of "SCRIPT_SRC_URL". Use this one when you need the name of the
script, for instance for relative self-references through URLs. Actually the same as
"SCRIPT_SRC_PATH_FILE", but provided for consistency.

"SCRIPT_SRC_SIZE"
The filesize of the script, in bytes.

"SCRIPT_SRC_MODIFIED"
The last modification time of the script, in seconds since 0 hours, 0 minutes, 0
seconds, January 1, 1970, Coordinated Universal Time.

"SCRIPT_SRC_MODIFIED_CTIME"
The last modification time of the script, in ctime(3) format (``WDAY MMM DD HH:MM:SS
YYYY\n'').

"SCRIPT_SRC_MODIFIED_ISOTIME"
The last modification time of the script, in ISO format (``DD-MM-YYYY HH:MM'').

"SCRIPT_SRC_OWNER"
The username of the script owner.

"VERSION_INTERPRETER"
The ePerl identification string.

"VERSION_LANGUAGE"
The identification string of the used Perl interpreter library.

Provided Built-In Images
The following built-in images can be accessed via URL "/url/to/nph-eperl/"NAME".gif":

"logo.gif"
The standard ePerl logo. Please do not include this one on your website.

"powered.gif"
The ``powered by ePerl 2.2'' logo. Feel free to use this on your website.

Use eperl online using onworks.net services