I'm not going to comment on the speed of either of these because I honestly don't know.
But, what I do know is that one of the wonderful things about perl is that it can be run on any system without recoding. With this in mind, I try to minimize the number of system (or backtick) calls I make. Since 'cat' is not a windows command, if you go with the first option your script will not run on a windows machine; however your second choice makes your script platform independent, and that is a wonderful thing.
