I have got the error:
Ambiguous call resolved as CORE::join(), qualify as such or use & at
When I fix error as:
$args = CORE::join( ', ', @$args );
everything works fine.
But when I fix it as:
$args = &join( ', ', @$args );
As suggested by error message, I got different error:
Can't locate object method "_make_instance" via package ", " (perhaps you forgot to load ", "?) at
why second fix does not work?
You're getting that warning because you've defined a subroutine called join. Now Perl isn't sure whether join( ', ', @$args ) is supposed to call the built-in function or your subroutine.
CORE::join unambiguously calls the built-in join.
&join(...) unambiguously calls your subroutine (and overrides any prototype it may have). As for why your subroutine throws bizarre errors about a package called , and _make_instance, we can't answer that if you don't show us the code.
You are getting the error because you have a sub named join, so you need to disambiguate it. To make it call the built-in, prepend CORE::. To make it call the sub, prepend &.
The error is because you are calling the sub and it is actually a method that is expecting an object or class as the first parameter, which would happen implicitly when you use the method call syntax.