"&" causes Perl to ignore the sub's prototype.
Some people use "&" to indicate a user sub, since it can only be used on subs, not on builtin functions. But I think that's a bad idea since "&" is not just decorative.
You might be interested in reading (tye)Re: A question of style.
In reply to Re^3: variable reference problem
by ikegami
in thread variable reference problem
by priyankgandhi
| For: | Use: | ||
| & | & | ||
| < | < | ||
| > | > | ||
| [ | [ | ||
| ] | ] |