#start the test case.
my $x= new blahblah;  # what I'm testing.
# The above and following method calls will be different for each test.
$x->foo (5000);
$x->bar(200);
# output_test is my common code I'll use i'll use to validate all the similar tests.
my $ot= output_test->new ("out1");  # ready... different name for each.
my $outfile= $ot->openout();  # get set... (common code to generate file name, open it for output, check for errors)
$x->emit ($outfile);  # this method call will differ for each test case, so it's not part of the common code.
$ot->ok_files_match();  # and back to the common code again to compare the resulting file with a reference "correct" file.

# do all that again, with differences.
# ...