Which brings us to another interesting question... What is the main difference between tr///? and s///? And I don't mean syntatically speaking!
Why would someone use one or the other in a specific case? I tend to be more of the sort that always uses s///'s. I have a bad habit of learning one way to do it, and sticking through with what I know works. (other examples would be the use of foreach instead of while, or !($var eq $val) instead of ($var ne $val) and I know the latter is the correct form...)