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.
Merge pull request #150 from bk2204/highlight-package-name

Fix highlighting for function name after print.