Add the following to the top:

use strict;
use warnings FATAL => 'all';
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Fix all the problems that arise. Your problems will be much clearer now.

As for your code, there are modules that deal with that. You really don't want to use eval. If you can't use modules for some reason, here's a version that should work for you (untested!):

sub get_numbers_from_ranges {
    my $spec = shift;

    my %numbers;
    foreach my $x ( split ',', $spec ) {
        if ( $x =~ /(\d+)-(\d+)/ ) {
            $numbers{$_} = undef for $1 .. $2;
        }
        else {
            $numbers{$x} = undef;
        }
    }
    return map { $_ - 1 } sort { $a <=> $b } keys %numbers;
}
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