|There's more than one way to do things|
I had some fun with this. My shortest fully-functional attempt is this 60-character regexp:
with these features:
Note that if we ignore two words (yttrium and ytterbium), we can safely bring it down to 52 chars:
And if we decide to switch to the dialect of pig latin that doesn't add 'w' on vowel-words, it's down to 44:
If I combine that with perlmonkey's attempt (losing a bit of functionality in the process, although it still works pretty well) I can reach 36:
Also note that my (un-golfed) attempt at a pig latin converter in Visual Basic took up almost 3500 characters (!) without handling nearly all of the exceptions mentioned here. This is (one of the many reasons) why I love Perl!
Thanks to everyone for their previous attempts, which helped me quite a bit. Comments are welcome.