It has nothing to do with lvalue functions. The same problem occurs if it's not an lvalue function.

Perl thinks you are using the ?...? operator (Look under "Quote and Quote-like Operators"). Omitting parens is dangerous.

Change
( META_HIDDEN ? "/.$newname." : "/$newname." )
to
( META_HIDDEN() ? "/.$newname." : "/$newname." )
or to
( (META_HIDDEN) ? "/.$newname." : "/$newname." )