Yeah, but that statement is a bit silly. Using all cap names doesn't avoid collision with other barewords. Typical barewords found in Perl programs are uppercase: file and directory handles. The other major category of barewords are in titlecase: package names. Barewords as in unquoted strings I only find in the student books of the Perl courses of HP Education.

Avoiding collisions with subroutine names? Come again? You know which subroutine names you are using, don't you? Besides, what if you do use subroutines, aren't you in grave danger of colliding with other subroutine names? No, of course not. It's not a problem for the set of subroutines in a program, and won't suddenly be a problem if you use lowercase constants.

Leaves us collisions with keywords. Well, you know which keywords there are, so it's easy to avoid them. The only potential problem you have is when you upgrade perl, new keywords might be introduced. Of course, you already have a problem because subroutine names can collide as well. But how common are new keywords in new versions of Perl anyway? In the last couple of yours, new keywords are our and lock, both introduced in 5.005. But in 5.005, we also saw the birth of INIT and in 5.6.0, CHECK was introduced. So, using all caps is as likely to cause a collision as to use all lowercase.

If you want to reduce the chance of collisions, you'd use names starting with a lowercase letter, and having one or more uppercase letters in them as well.

Abigail