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PROGRAM:
NAME
perlcheat - Perl 5 Cheat Sheet
DESCRIPTION
This 'cheat sheet' is a handy reference, meant for beginning Perl programmers. Not
everything is mentioned, but 195 features may already be overwhelming.
The sheet
CONTEXTS SIGILS ref ARRAYS HASHES
void $scalar SCALAR @array %hash
scalar @array ARRAY @array[0, 2] @hash{'a', 'b'}
list %hash HASH $array[0] $hash{'a'}
&sub CODE
*glob GLOB SCALAR VALUES
FORMAT number, string, ref, glob, undef
REFERENCES
\ reference $$foo[1] aka $foo->[1]
$@%&* dereference $$foo{bar} aka $foo->{bar}
[] anon. arrayref ${$$foo[1]}[2] aka $foo->[1]->[2]
{} anon. hashref ${$$foo[1]}[2] aka $foo->[1][2]
\() list of refs
SYNTAX
OPERATOR PRECEDENCE foreach (LIST) { } for (a;b;c) { }
-> while (e) { } until (e) { }
++ -- if (e) { } elsif (e) { } else { }
** unless (e) { } elsif (e) { } else { }
! ~ \ u+ u- given (e) { when (e) {} default {} }
=~ !~
* / % x NUMBERS vs STRINGS FALSE vs TRUE
+ - . = = undef, "", 0, "0"
<< >> + . anything else
named uops == != eq ne
< > <= >= lt gt le ge < > <= >= lt gt le ge
== != <=> eq ne cmp ~~ <=> cmp
&
| ^ REGEX MODIFIERS REGEX METACHARS
&& /i case insensitive ^ string begin
|| // /m line based ^$ $ str end (bfr \n)
.. ... /s . includes \n + one or more
?: /x ignore wh.space * zero or more
= += last goto /p preserve ? zero or one
, => /a ASCII /aa safe {3,7} repeat in range
list ops /l locale /d dual | alternation
not /u Unicode [] character class
and /e evaluate /ee rpts \b boundary
or xor /g global \z string end
/o compile pat once () capture
DEBUG (?:p) no capture
-MO=Deparse REGEX CHARCLASSES (?#t) comment
-MO=Terse . [^\n] (?=p) ZW pos ahead
-D## \s whitespace (?!p) ZW neg ahead
-d:Trace \w word chars (?<=p) ZW pos behind \K
\d digits (?<!p) ZW neg behind
CONFIGURATION \pP named property (?>p) no backtrack
perl -V:ivsize \h horiz.wh.space (?|p|p)branch reset
\R linebreak (?<n>p)named capture
\S \W \D \H negate \g{n} ref to named cap
\K keep left part
FUNCTION RETURN LISTS
stat localtime caller SPECIAL VARIABLES
0 dev 0 second 0 package $_ default variable
1 ino 1 minute 1 filename $0 program name
2 mode 2 hour 2 line $/ input separator
3 nlink 3 day 3 subroutine $\ output separator
4 uid 4 month-1 4 hasargs $| autoflush
5 gid 5 year-1900 5 wantarray $! sys/libcall error
6 rdev 6 weekday 6 evaltext $@ eval error
7 size 7 yearday 7 is_require $$ process ID
8 atime 8 is_dst 8 hints $. line number
9 mtime 9 bitmask @ARGV command line args
10 ctime 10 hinthash @INC include paths
11 blksz 3..10 only @_ subroutine args
12 blcks with EXPR %ENV environment
ACKNOWLEDGEMENTS
The first version of this document appeared on Perl Monks, where several people had useful
suggestions. Thank you, Perl Monks.
A special thanks to Damian Conway, who didn't only suggest important changes, but also
took the time to count the number of listed features and make a Perl 6 version to show
that Perl will stay Perl.
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