That's true, for the specific case I gave -M is simpler. The only thing to note is that -M doesn't use time(). It uses script start time. So in a long running process it may not be what you want:

$ perl -e ' print -M "/usr/bin","\n"; sleep(120); print -M "/usr/bin",
+"\n"'
5.9218287037037
5.9218287037037
[download]

Thanks, I didn't realize I was responding to a question that has already been thoroughly answered.