while (<DATA>) {

        chomp;
        print "Test case '$_'\n";

        if (  m!^(-?\d+)\s+(-?\d+)!  )
        {
                print "$_, " for ($1 .. $2);
        }
        else
        {
                print "doesn't match";
        }

        print "\n\n";

}

__DATA__
1 6
-4 6
-4 -1
6 1
6 -4
-1 -4