Fix highlighting for function name after print.

Previously, "Foo" was highlighted in the following:

  print Foo::Bar::baz();

When trying to match a bareword as a filehandle, ensure that the match ends at
the end of a keyword to rule out accidentally matching the beginning part of a
fully-qualified function name.

This does result in three differences in the corpus; however, they are all exactly this case and they are now correctly highlighted. I happened to notice this today at work because we use a lot of fully-qualified function names.