Get rid of the hash, at least for storing the numbers. I presume you need it to ensure numbers are unique if ranges overlap. I'd do something like:

use strict;
use warnings;

my @nums = get_numbers_from_ranges ('2,10-13,2-5');

print "@nums";

sub get_numbers_from_ranges {
    my @ranges = split ',', shift;
    my @numbers;
    my %seen;

    for my $range (@ranges) {
        my ($start, $end) = sort {$a <=> $b} split '-', $range;
        
        $end ||= $start;
        ! $seen{$_}++ and push @numbers, $_ for $start .. $end;
    }

    return @numbers;
}
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Prints:

2 10 11 12 13 3 4 5
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