I had some thoughts regarding the regexes in this function. The second substitution seems to be eliminating dots and dashes from the begining of a file name. This is understandable on *nix so that no "dot files" or hidden files are created. I would however change the line from this:

$filename=~ s/^[-.]//;
[download]

to this:

$filename=~ s/^[-.]*//;
[download]

This way, all of the dots and dashes at the start of the filename are eliminated. Consider the case where $filename is equal to "..filename"