Blocks of grep & map were simple enough, which could have been combined simply, notwithstanding my lack of attention to ...

Thanks for pointing out the bug the fifth time that I had missed in my zeal to curb the extravagance.

I would rather have then map { $f = "$dir/$_" ; -f $f ? ... } ..., though some may find "$f" to be excessive. (By this time I would have busted out File::Find already to be honest.)