Linux Ask! is a Q & A web site specific for Linux related questions. Questions are collected, answered and audited by experienced Linux users.
Generate new list using map in Perl
Answer:
The Perl's map function is superb cool for generating new list based on an existing list.
1. Generate new array based on an existing array
my @new = map {$_ * 2} (1, 2, 3);
# @new contains 2, 4, 6
2. Generate new hash based on an existing array
my %new = map {$_ => 1} (1,2,3);
# %new contains a hash...
# {
# '1' => 1,
# '3' => 1,
# '2' => 1
# };
Filter a list using grep in Perl
Answer:
The Perl's grep function is very useful for list filtering.
E.g. Array filtering
my @new = grep {$_ > 1} (1,2,3);
# @new contains 2, 3 only
Simple try catch block in Perl
Answer:
Perl don't have try/catch statement by default, but you can simulate using the following way:
eval {
print 1/0;
};
if ($@) {
print "Error message: $@";
};
When executed, it shows:
Error message: Illegal division by zero at test.pl line 7.
Array reference in Perl
Answer:
Array reference is something like a pointer to a array data structure in Perl
Example:
use strict;
use warnings;
my @a = (1, 2, 3);
my $array_ref = \@a;
$a[2] = "foo";
print $array_ref->[2]; # print out "foo" as change in @a will also be reflected in its reference
Hash reference in Perl
Answer:
Hash reference is something like a pointer to a hash data structure in Perl
Example:
my %hash = (
"a" => "1",
"b" => "2",
);
my $hash_ref = \%hash;
$hash{"a"} = "A";
print $hash_ref->{"a"}; # print out "A" as change in %hash also reflected in its reference
