But that's only an issue if you keep the filehandles around, isn't it? You can open lots and lots of files without an explicit close() and I'm not sure where explicitly closing files is better than just having the filehandle get re-opened or fall out of scope:
I like explicit closes. I like explicit lots of things that Perl auto-does if given a chance.
On the maintainability front, an explicit close() tells the maintainer that the author "meant to do that" and "here". No explicit close leaves questions. Did they mean to let it close automagically, or did they leave out the close where they really wanted it, etc.
I rarely have the luxury of working with expert Perl programmers. The more that's done explicitly and clearly, the better for everyone involved.