#!/usr/bin/perl
use strict;
use warnings;
use diagnostics;
use Data::Dumper;

use Scalar::Util qw(looks_like_number);

my $text = '1-20,1,1,1,2,4,5,8,9,3-4';

my $list = &_text_to_list($text);
print Dumper $list;
exit;

sub _text_to_list
  #
{
    my @list = split( ',', shift );
    my %hash;

    for ( 0 .. $#list ) {
        if ( $list[$_] =~ /(.*)-(.*)/ ) {
            $hash{$_} = 1 for $1 .. $2;
            next;
        }
        $hash{ $list[$_] } = 1 if looks_like_number( $list[$_] );
    }

    @list = ();
    push @list, $_ for keys %hash;
    return \@list;
}