Perl sort

last modified October 8, 2026

The Perl sort operator takes a list and returns its elements in sorted order. By default, it compares values as strings. A comparison block lets you choose a numeric, reverse, or application-specific order.

sort returns a sorted list; it does not rearrange the source array. Assign the result to an array when you want to keep the sorted values.

Default string sorting

Without a comparison block, values are sorted in string (lexical) order.

strings.pl

#!/usr/bin/perl

use strict;
use warnings;
use v5.30.0;

my @names = ('Pear', 'apple', 'plum', 'Banana');
my @sorted = sort @names;

say "@sorted";

$ perl strings.pl
Banana Pear apple plum

String comparison is case-sensitive. It compares character values rather than treating digit-containing strings as numbers.

Numeric sorting

Use the numeric comparison operator <=> to sort numbers in ascending order. The comparator's result is negative, zero, or positive when $a is less than, equal to, or greater than $b.

numbers.pl

#!/usr/bin/perl

use strict;
use warnings;
use v5.30.0;

my @numbers = (40, 3, 100, 12, 3);
my @ascending = sort { $a <=> $b } @numbers;
my @descending = sort { $b <=> $a } @numbers;

say "ascending:  @ascending";
say "descending: @descending";

$ perl numbers.pl
ascending:  3 3 12 40 100
descending: 100 40 12 3 3

$a and $b are special package variables supplied to the sort comparator. They are exempt from strict 'vars'; do not declare them with my.

Custom string sorting

A comparator can apply a transformation before comparing. This example sorts names without regard to letter case:

case_insensitive.pl

#!/usr/bin/perl

use strict;
use warnings;
use v5.30.0;

my @names = ('Pear', 'apple', 'plum', 'Banana');
my @sorted = sort { lc($a) cmp lc($b) } @names;

say "@sorted";

$ perl case_insensitive.pl
apple Banana Pear plum

For locale-aware ordering or language-specific collation, use a suitable collation module rather than assuming lc plus cmp implements every language's sorting rules.

Sorting records by a field

References allow a list to contain structured records. Dereference the records in the comparator to choose a field.

records.pl

#!/usr/bin/perl

use strict;
use warnings;
use v5.30.0;

my @people = (
    { name => 'Grace', age => 85 },
    { name => 'Ada',   age => 36 },
    { name => 'Linus', age => 55 },
);

my @by_age = sort { $a->{age} <=> $b->{age} } @people;
say "$_->{name}: $_->{age}" for @by_age;

$ perl records.pl
Ada: 36
Linus: 55
Grace: 85

Sorting keys and preserving the original

Hash iteration order is not a presentation order. Sort the keys when displaying their associated values.

use strict;
use warnings;
use v5.30.0;

my %scores = (Mira => 91, Alex => 84, Jo => 97);

for my $name (sort keys %scores) {
    say "$name: $scores{$name}";
}

To sort an array without changing it, keep the result in a different array:

my @original = (4, 1, 3);
my @ordered = sort { $a <=> $b } @original;

See Perl map for transforming lists and Perl hash for working with hash keys and values.

Source

Perl sort documentation

Author

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