Might be worth mentioning that for pretty much anything that you do with paths internal to perl, you can use "c:/tmp/sup/$filename" which is a lot easier on the eyes than "c:\\tmp\\sup\\$filename".

You can also get away with coding 'c:\tmp\sup' . $filename where you need constants that are going to be passed to CMD.EXE or other uncooperative .exe's, so long as you use single quotes.