My guess is that any dereferencing overhead is invisible next to the overhead of constructing scalars and then stringifying them.

As for the performance issue, the general programming principle is that premature optimization is the root of all evil. Furthermore if performance really is critical, then Perl is the wrong language to use. Perl will speed development, has very large reusable libraries, improves reliability by doing memory management for you, etc, etc, etc. But while it is fast for a scripting language, far faster ones exist out there.