#!/usr/bin/perl -wl
use strict;

my @a=0..1e3;       # Set higher than any reasonable message number
my @list = ("1, 3, 5-7", "1-5, 2, 4", "1-3, 2-5");

for (@list){
    my %h;
    s/-/../g;
    $h{$_}++ for @a[(eval $_)];
    print join " ", sort {$a<=>$b} keys %h;
}