PERLCHEAT(1) | Perl Programmers Reference Guide | PERLCHEAT(1)

# 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 /xx ign. 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 Raku version to show that Perl will stay Perl.

# AUTHOR

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

# SEE ALSO

- <https://perlmonks.org/?node_id=216602> - the original PM post
- <https://perlmonks.org/?node_id=238031> - Damian Conway's Raku version
- <https://juerd.nl/site.plp/perlcheat> - home of the Perl Cheat Sheet

2021-03-02 | perl v5.40.1