perlcheat - Perl 5 Cheat 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