There are many times when this is useful. This might not be the best example but it is one possible use. In this case to do a substitution in each array entry. I think a bigger point would be that you have found your way to "use strict". A definate thing you should always do.
THRAK
Comment on Re: Simple question about foreach and my.
You need to be very careful using this idiom, especially
if you're hoing to embed loops. It's very easy to mix up
which $_ belongs to which loop and create
some horrendous problems.
In general I find it's better to name (and declare)
the iteration variables unless it's really going to
be a short loop (in which case I tend to use the statement
modifier expr for (@array) in any case)