Just a quick note that, despite what many have appeared to assume, this may not be a question about the "grep" program as the noder refers to it as "the GREP function". It may simply be that the noder doesn't understand that Perl's grep works on a list of scalars (not on filenames) and requires either braces or a comma (or that was left out when the example was retyped).

jjdeterick should definitely take more care in crafting future questions (cutting and pasting the exact code involved and exactly what output and/or error is generated).