To the cause of your specific problem, the line:

while (readdir (DIR)) {

does not magically assign to $_, so for a quick fix you could change it to

while ($_ = readdir (DIR)) {

You'll be much closer to what you want.

I guess you never saw any of your debug messages that indicated that no files were ever tested in your loop. ;-)

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I'd like to be able to assign to an luser