Everyone has gave you some good replies but here is a resource that comes from, the horse's mouth, Larry Wall.

Programming PERL 2nd Edition
Chapter 8
Topic "Programming with Style"

"The most important thing is to run your programs under the -w flag at all times. You may turn it off specifically for particular portions of code via the $^W variable if you must. You should also always run under strict or know the reason why not. The use sigtrap and even use diagnostics pragmas may also prove of benefit."

That pretty much says it all!

Good Luck