Perl, short version Cheat Sheet

A Programming › Perl cheat sheet in English by mishin

long version construction and short analog in Perl

18,549 views 5,874 downloads 16 Jul 2012 History

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Hash Slices

use Modern::Perl;
my $input_line = shift;

my %colors = (
red => 'apple',
green => 'leaves',
blue => 'ocean',
);

$colors{"red"} = 'apple';
$colors{"green"} = 'leaves';
$colors{"blue"} = 'ocean';

( $colors{"red"}, $colors{"green"}, $colors{"blue"} ) =
( 'apple', 'leaves', 'ocean' );

@colors{ "red", "green", "blue" } = ( 'apple', 'leaves', 'ocean' );
my @avaible_colors = qw(red green blue);
my @avaible_things = qw(apple leaves ocean);

@colors{@avaible_colors} = @avaible_things;#1
#for ref
my $ref_colors = \%colors;
@{$ref_colors}{@avaible_colors} = @avaible_things;#the same as 1 but for ref

say $colors{$input_line};
say ${$ref_colors}{$input_line};
say "@{$ref_colors}{@avaible_colors}";

# http://docstore.mik.ua/orelly/perl/learn/ch05_05.htm
# http://www.webquills.net/web-development/perl/perl-5-hash-slices-can-replace.html

Perl short tips

Merge Hash slow (merge %score into %league)

%league = (%league, %score);

Merge Hash faster

%league{keys %score} = values %score;

Write array to file. use File::Slurp qw( :std );

my @vip_array_out = map { "$_\n" } @vip_array;

the same

my $vip_string_out = join "\n", @vip_array;

slow

write_file( 'file', @vip_array_out );#

faster

write_file( 'file', \@vip_array_out );#

faster then $vip_string_out

write_file( 'file', \$vip_string_out );

Split by WORD

my @words = split /\W+/, @input_lines;

Get unique words

my %seen; map { $seen{$_}++ } @words;

Sort the words in ascending ASCII order in the output

for my $word ( sort keys %seen ) { say "for $word $seen{$word}"; }

Save hash in insert order

use Tie::IxHash;

tie %sort_seen, "Tie::IxHash";

use Data::Dumper;

$Data::Dumper::Terse = 1;

map { $sort_seen{$_} = $seen{$_} } sort keys %seen;

print Dumper \%sort_seen;

Read config

use YAML::Tiny;
use Carp;
use English;
my $conf =
YAML::Tiny::LoadFile('config.yml')
or croak "Couldn't open YAML::Tiny->errstr: $OS_ERROR";

my $user = $conf->{user};
my $password = $conf->{password};

config.yml is
---
user: 'mishin'
password: 'secret_pw'

Slices

array slice

($him, $her) = @folks[0,-1];

@them = @folks[0 .. 3];

hash slice

($who, $home) = @ENV{"USER", "HOME"};

list slice

($uid, $dir) = (getpwnam("daemon"))[2,7];

@days[3..5] = qw/Wed Thu Fri/;

@colors{'red','blue','green'} = (0xff0000, 0x0000ff, 0x00ff00);

@folks[0, -1] = @folks[-1, 0];

http://perldoc.perl.org/perldata.html#Slices

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