You don't check every operation for success. You should check that readdir worked:

@thefiles= readdir(IMD) or die "can't readdir: $!";
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And the most important part : check that you can actually "move" the files:

system qq(move /y "$defaultdir/$text" "$destinationdir") or die "can't
+ move the file: $!";
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to understand where exactly the script fails.