I think more than localizing the dir handle is needed to get it to work.
Fastolfe already gave the best answer.
Now some other trouble with the original code

if ($tmp =~ /\.\.?/) { next; }
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This will skip any file with one or two periods. This might cause trouble at the mill.

$tmp = "$dir/$tmp";
if ($tmp =~ /^(\w*)\.(jpg|jpeg)$/)
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\w will only match letters and _. You put a / in.