Or you could let Number::Range do it for you:

use strict;
use warnings;

use Test::More;
use Number::Range;

sub get_numbers_from_ranges {
  my @ranges = split ',', shift;
  my @numbers = ();
  for my $range (@ranges) {
    my ($start, $end) = split '-', $range;
    push @numbers, ($end)
      ? Number::Range->new("$start..$end")->range()
      : $start;
  }
  return \@numbers;
}

plan tests => 2;

is_deeply(
  get_numbers_from_ranges("2-8,10-13,18"),
  [ 2, 3, 4, 5, 6, 7, 8, 10, 11, 12, 13, 18 ]
);
is_deeply(
  get_numbers_from_ranges("6-9,1-3,11"), 
  [ 6, 7, 8, 9, 1, 2, 3, 11 ]);

__END__
[download]

$ prove  713553.pl
713553....ok
All tests successful.
Files=1, Tests=2,  0 wallclock secs ( 0.04 cusr +  0.01 csys =  0.05 C
+PU)
[download]