Re^3: To & or not to & ?

[!1]

because only one of them does something different than FUNC()

Actually, all of them do something different as shown below:

> perl -le'@_=2;sub a($$) {shift or 1};print &a'
2
> perl -le'@_=2;sub a($$) {shift or 1};print &a()'
1
> perl -le'@_=2;sub a($$) {shift or 1};print a()'
Not enough arguments for main::a at -e line 1, at end of line
Execution of -e aborted due to compilation errors.

Sorry for the pedantry.