ken@ganymede: ~/tmp/PM_DIFF $ cat a.txt b.txt c.txt dummy.txt d.txt ken@ganymede: ~/tmp/PM_DIFF $ cat b.txt Hello hello hello, world goodbye ken@ganymede: ~/tmp/PM_DIFF $ cat c.txt hello world hullo shellow ken@ganymede: ~/tmp/PM_DIFF $ cat d.txt hello, world hello and goodbye Hello, world ken@ganymede: ~/tmp/PM_DIFF $ cat result.list ken@ganymede: ~/tmp/PM_DIFF $ pm_diff.pl Enter reference filename: not_a_file Can't open not_a_file: No such file or directory at ./pm_diff.pl line 13, line 1. ken@ganymede: ~/tmp/PM_DIFF $ cat result.list ken@ganymede: ~/tmp/PM_DIFF $ pm_diff.pl Enter reference filename: a.txt PROCESSING: b.txt PROCESSING: c.txt ! SKIPPING: dummy.txt: No such file or directory at ./pm_diff.pl line 19, <$fh_ref> line 3. PROCESSING: d.txt ken@ganymede: ~/tmp/PM_DIFF $ cat result.list [b.txt] hello [b.txt] hello, world [c.txt] hello world [c.txt] shellow [d.txt] hello and goodbye ken@ganymede: ~/tmp/PM_DIFF $