perlcheat - Perl 5 Cheat Sheet


   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
     \      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
     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    *      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  	     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    (?|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
     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


   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.


   Juerd Waalboer <>, with the help of many Perl Monks.


   *   <> - the original PM post

   *   <> - Damian Conway's Perl 6

   *   <> - home of the Perl Cheat Sheet


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