as you're using "warnings", there is not point calling "perl -w"There is a difference, from perldoc warnings:
The warnings pragma is a replacement for the command line flag -w , but the pragma is limited to the enclosing block, while the flag is global. See perllexwarn for more information.-w does everything warnings does, not the other way around. That being said, it is unlikely the OP wants to enable warnings for use'd modules (XML::Parser, etc.).