What I fail to understand is why it worked under perl 5.8. The purpose of taint mode is to capture potentially dangerous information before it affects your machine or you. Writing to a file handle (which could be any thing from your /etc/passwd to a socket to your bank's webserver) comes into that category. My suspicion is that from time to time you turn off taint mode on development machines (as I do) and this muddied the waters.