You want Set::IntSpan. The only way I know this is that newsrc files use that format, and that's what News::Newsrc uses. :)

Update: bobf notes that Set::IntSpan needs a run in increasing order, and that most solutions pretty much do the same thing that I've done below. However, I'm thinking about the next part of the problem, where some part of the program is going to ask if a value is in that list. Making the range is easy with simple Perl. Getting data out of it is a bit more complicated. :)

#!/usr/bin/perl

use Set::IntSpan;


while( <DATA> )
    {
    chomp;
    my $set = Set::IntSpan->new(
        join ",",
        sort { $a <=> $b }
        split /,/, $_
        );
        
    print "$_  --->  @{ [ $set->elements] }\n";
    }
    
__END__
80
17-199
18,512,21,78
18,5,1790,19-66,212,213
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