in reply to dbmopen - if db file do this else do that

short of writing for both .db and .dir/.pag can a monk enlighten me?

There's no easy answer to this one. The file extension is going to depend on the versio of DBM that Perl is linked with. If you're only worried about the pair of platforms, set $extension based on testing $^O (OSNAME). And you can avoid the overhead of open() by using -f.

In Section Seekers of Perl Wisdom