Handle array refs.
Add a comment explaining the meaning of $/ special variable.

So future reader will know what does it mean without running "perldoc
perlvar".
Return plain booleans in validation methods.

Users of validate_* passing "0" might get failures on correct name
because of coercion of "0" to false in code like:

die_error(500, "invalid ref") unless (check_ref_format ("0"));

This is to avoid coercion of correct input like "0" into false resulting