#!/usr/bin/perl

while (<>) {
        print if m!(^-{0,1}\d*)\s+(\d*)!m;
        print "$_\n" for ($1 .. $2);
        }

But when I allow both to be negative it doesn't:

#!/usr/bin/perl

while (<>) {

        print if m!(^-{0,1}\d*)\s+(^-{0,1}\d*)!m;
        print "$_\n" for ($1 .. $2);
        }