Perl 5 version 22.4 documentation

perlcheat

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

  1.   CONTEXTS  SIGILS  ref        ARRAYS        HASHES
  2.   void      $scalar SCALAR     @array        %hash
  3.   scalar    @array  ARRAY      @array[0, 2]  @hash{'a', 'b'}
  4.   list      %hash   HASH       $array[0]     $hash{'a'}
  5.             &sub    CODE
  6.             *glob   GLOB       SCALAR VALUES
  7.                     FORMAT     number, string, ref, glob, undef
  8.   REFERENCES
  9.   \      reference       $$foo[1]       aka $foo->[1]
  10.   $@%&*  dereference     $$foo{bar}     aka $foo->{bar}
  11.   []     anon. arrayref  ${$$foo[1]}[2] aka $foo->[1]->[2]
  12.   {}     anon. hashref   ${$$foo[1]}[2] aka $foo->[1][2]
  13.   \()    list of refs
  14.                          SYNTAX
  15.   OPERATOR PRECEDENCE    foreach (LIST) { }     for (a;b;c) { }
  16.   ->                     while   (e) { }        until (e)   { }
  17.   ++ --                  if      (e) { } elsif (e) { } else { }
  18.   **                     unless  (e) { } elsif (e) { } else { }
  19.   ! ~ \ u+ u-            given   (e) { when (e) {} default {} }
  20.   =~ !~
  21.   * / % x                 NUMBERS vs STRINGS  FALSE vs TRUE
  22.   + - .                   =          =        undef, "", 0, "0"
  23.   << >>                   +          .        anything else
  24.   named uops              == !=      eq ne
  25.   < > <= >= lt gt le ge   < > <= >=  lt gt le ge
  26.   == != <=> eq ne cmp ~~  <=>        cmp
  27.   &
  28.   | ^             REGEX MODIFIERS       REGEX METACHARS
  29.   &&              /i case insensitive   ^      string begin
  30.   || //           /m line based ^$      $      str end (bfr \n)
  31.   .. ...          /s . includes \n      +      one or more
  32.   ?:              /x ignore wh.space    *      zero or more
  33.   = += last goto  /p preserve           ?      zero or one
  34.   , =>            /a ASCII    /aa safe  {3,7}  repeat in range
  35.   list ops        /l locale   /d  dual  |      alternation
  36.   not             /u Unicode            []     character class
  37.   and             /e evaluate /ee rpts  \b     boundary
  38.   or xor          /g global             \z     string end
  39.                   /o compile pat once   ()     capture
  40.   DEBUG                                 (?:p)  no capture
  41.   -MO=Deparse     REGEX CHARCLASSES     (?#t)  comment
  42.   -MO=Terse       .   [^\n]             (?=p)  ZW pos ahead
  43.   -D##            \s  whitespace        (?!p)  ZW neg ahead
  44.   -d:Trace        \w  word chars        (?<=p) ZW pos behind \K
  45.                   \d  digits            (?<!p) ZW neg behind
  46.   CONFIGURATION   \pP named property    (?>p)  no backtrack
  47.   perl -V:ivsize  \h  horiz.wh.space    (?|p|p)branch reset
  48.                   \R  linebreak         (?<n>p)named capture
  49.                   \S \W \D \H negate    \g{n}  ref to named cap
  50.                                         \K     keep left part
  51.   FUNCTION RETURN LISTS
  52.   stat      localtime    caller         SPECIAL VARIABLES
  53.    0 dev    0 second      0 package     $_    default variable
  54.    1 ino    1 minute      1 filename    $0    program name
  55.    2 mode   2 hour        2 line        $/    input separator
  56.    3 nlink  3 day         3 subroutine  $\    output separator
  57.    4 uid    4 month-1     4 hasargs     $|    autoflush
  58.    5 gid    5 year-1900   5 wantarray   $!    sys/libcall error
  59.    6 rdev   6 weekday     6 evaltext    $@    eval error
  60.    7 size   7 yearday     7 is_require  $$    process ID
  61.    8 atime  8 is_dst      8 hints       $.    line number
  62.    9 mtime                9 bitmask     @ARGV command line args
  63.   10 ctime               10 hinthash    @INC  include paths
  64.   11 blksz               3..10 only     @_    subroutine args
  65.   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.

AUTHOR

Juerd Waalboer <#####@juerd.nl>, with the help of many Perl Monks.

SEE ALSO