I don't yet remember all of the characters that have special meanings inside a regex (as it sounds like "&" does: to ignore prototypes?).

The  & (ampersand) character is not a regular expression metacharacter, i.e., it has no special meaning in a regex.

The  & sigil does have a special meaning with respect to subroutine invocation. See perlsub and search for '&', especially in the first part of the DESCRIPTION section.