[perl5.git] / pod / perlcheat.pod

=head1 NAME

perlcheat - Perl 5 Cheat Sheet

=head1 DESCRIPTION

This 'cheat sheet' is a handy reference, meant for beginning Perl
programmers. Not everything is mentioned, but 194 features may
already be overwhelming.

=head2 The sheet

  CONTEXTS  SIGILS             ARRAYS        HASHES
  void      $scalar   whole:   @array        %hash
  scalar    @array    slice:   @array[0, 2]  @hash{'a', 'b'}
  list      %hash     element: $array[0]     $hash{'a'}
            &sub
            *glob    SCALAR VALUES
                     number, string, reference, glob, undef
  REFERENCES
  \     references      $$foo[1]       aka $foo->[1]
  $@%&* dereference     $$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
                          NUMBERS vs STRINGS  LINKS
  OPERATOR PRECEDENCE     =          =        perl.plover.com
  ->                      +          .        search.cpan.org
  ++ --                   == !=      eq ne         cpan.org
  **                      < > <= >=  lt gt le ge   pm.org
  ! ~ \ u+ u-             <=>        cmp           tpj.com
  =~ !~                                            perldoc.com
  * / % x                 SYNTAX
  + - .                   for    (LIST) { }, for (a;b;c) { }
  << >>                   while  ( ) { }, until ( ) { }
  named uops              if     ( ) { } elsif ( ) { } else { }
  < > <= >= lt gt le ge   unless ( ) { } elsif ( ) { } else { }
  == != <=> eq ne cmp     for equals foreach (ALWAYS)
  &
  | ^              REGEX METACHARS            REGEX MODIFIERS
  &&               ^     string begin         /i case insens.
  ||               $     str. end (before \n) /m line based ^$
  .. ...           +     one or more          /s . includes \n
  ?:               *     zero or more         /x ign. wh.space
  = += -= *= etc.  ?     zero or one          /g global
  , =>             {3,7} repeat in range
  list ops         ()    capture          REGEX CHARCLASSES
  not              (?:)  no capture       .  == [^\n]
  and              []    character class  \s == [\x20\f\t\r\n]
  or xor           |     alternation      \w == [A-Za-z0-9_]
                   \b    word boundary    \d == [0-9]
                   \z    string end       \S, \W and \D negate
  DO
  use strict;        DON'T            LINKS
  use warnings;      "$foo"           perl.com
  my $var;           $$variable_name  perlmonks.org
  open() or die $!;  `$userinput`     use.perl.org
  use Modules;       /$userinput/     perl.apache.org
                                      parrotcode.org
  FUNCTION RETURN LISTS
  stat      localtime    caller         SPECIAL VARIABLES
   0 dev    0 second     0 package      $_    default variable
   1 ino    1 minute     1 filename     $0    program name
   2 mode   2 hour       2 line         $/    input separator
   3 nlink  3 day        3 subroutine   $\    output separator
   4 uid    4 month-1    4 hasargs      $|    autoflush
   5 gid    5 year-1900  5 wantarray    $!    sys/libcall error
   6 rdev   6 weekday    6 evaltext     $@    eval error
   7 size   7 yearday    7 is_require   $$    process ID
   8 atime  8 is_dst     8 hints        $.    line number
   9 mtime               9 bitmask      @ARGV command line args
  10 ctime  just use                    @INC  include paths
  11 blksz  POSIX::      3..9 only      @_    subroutine args
  12 blcks  strftime!    with EXPR      %ENV  environment

=head1 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.

=head1 AUTHOR

Juerd Waalboer <juerd@cpan.org>, with the help of many Perl Monks.

=head1 SEE ALSO

 http://perlmonks.org/?node_id=216602      the original PM post
 http://perlmonks.org/?node_id=238031      Damian Conway's Perl 6 version
 http://juerd.nl/site.plp/perlcheat        home of the Perl Cheat Sheet
Commit	Line	Data
8fd8d6f4 JW	1	=head1 NAME
	2
	3	perlcheat - Perl 5 Cheat Sheet
	4
	5	=head1 DESCRIPTION
	6
	7	This 'cheat sheet' is a handy reference, meant for beginning Perl
	8	programmers. Not everything is mentioned, but 194 features may
	9	already be overwhelming.
	10
	11	=head2 The sheet
	12
	13	CONTEXTS SIGILS ARRAYS HASHES
	14	void $scalar whole: @array %hash
	15	scalar @array slice: @array[0, 2] @hash{'a', 'b'}
	16	list %hash element: $array[0] $hash{'a'}
	17	&sub
	18	*glob SCALAR VALUES
	19	number, string, reference, glob, undef
	20	REFERENCES
	21	\ references $$foo[1] aka $foo->[1]
	22	$@%&* dereference $$foo{bar} aka $foo->{bar}
	23	[] anon. arrayref ${$$foo[1]}[2] aka $foo->[1]->[2]
	24	{} anon. hashref ${$$foo[1]}[2] aka $foo->[1][2]
	25	\() list of refs
	26	NUMBERS vs STRINGS LINKS
	27	OPERATOR PRECEDENCE = = perl.plover.com
	28	-> + . search.cpan.org
	29	++ -- == != eq ne cpan.org
	30	** < > <= >= lt gt le ge pm.org
	31	! ~ \ u+ u- <=> cmp tpj.com
	32	=~ !~ perldoc.com
	33	* / % x SYNTAX
	34	+ - . for (LIST) { }, for (a;b;c) { }
	35	<< >> while ( ) { }, until ( ) { }
	36	named uops if ( ) { } elsif ( ) { } else { }
	37	< > <= >= lt gt le ge unless ( ) { } elsif ( ) { } else { }
	38	== != <=> eq ne cmp for equals foreach (ALWAYS)
	39	&
	40	\| ^ REGEX METACHARS REGEX MODIFIERS
	41	&& ^ string begin /i case insens.
	42	\|\| $ str. end (before \n) /m line based ^$
	43	.. ... + one or more /s . includes \n
	44	?: * zero or more /x ign. wh.space
	45	= += -= *= etc. ? zero or one /g global
	46	, => {3,7} repeat in range
	47	list ops () capture REGEX CHARCLASSES
	48	not (?:) no capture . == [^\n]
	49	and [] character class \s == [\x20\f\t\r\n]
	50	or xor \| alternation \w == [A-Za-z0-9_]
	51	\b word boundary \d == [0-9]
	52	\z string end \S, \W and \D negate
	53	DO
	54	use strict; DON'T LINKS
	55	use warnings; "$foo" perl.com
	56	my $var; $$variable_name perlmonks.org
	57	open() or die $!; `$userinput` use.perl.org
	58	use Modules; /$userinput/ perl.apache.org
	59	parrotcode.org
	60	FUNCTION RETURN LISTS
	61	stat localtime caller SPECIAL VARIABLES
	62	0 dev 0 second 0 package $_ default variable
	63	1 ino 1 minute 1 filename $0 program name
	64	2 mode 2 hour 2 line $/ input separator
65	3 nlink 3 day 3 subroutine $\ output separator
66	4 uid 4 month-1 4 hasargs $\| autoflush
67	5 gid 5 year-1900 5 wantarray $! sys/libcall error
68	6 rdev 6 weekday 6 evaltext $@ eval error
69	7 size 7 yearday 7 is_require $$ process ID
70	8 atime 8 is_dst 8 hints $. line number
71	9 mtime 9 bitmask @ARGV command line args
72	10 ctime just use @INC include paths
73	11 blksz POSIX:: 3..9 only @_ subroutine args
74	12 blcks strftime! with EXPR %ENV environment
75
76	=head1 ACKNOWLEDGEMENTS
77
78	The first version of this document appeared on Perl Monks, where several
79	people had useful suggestions. Thank you, Perl Monks.
80
81	A special thanks to Damian Conway, who didn't only suggest important changes,
82	but also took the time to count the number of listed features and make a
83	Perl 6 version to show that Perl will stay Perl.
84
85	=head1 AUTHOR
86
87	Juerd Waalboer <juerd@cpan.org>, with the help of many Perl Monks.
88
89	=head1 SEE ALSO
90
91	http://perlmonks.org/?node_id=216602 the original PM post
92	http://perlmonks.org/?node_id=238031 Damian Conway's Perl 6 version
93	http://juerd.nl/site.plp/perlcheat home of the Perl Cheat Sheet