I used the recommended goto SUB way. Here’s what happens.

There are two programs, in both debug is a fancy little debug message printer. In one of them, _debug is an actual sub that does a little more than this, it also sends the debug message to a server for central logging. In the other app, _debug is just an alias, so any case of _debug will still work: *_debug = \&debug;

Now, in the app that has the actual sub _debug { ... } declared, Perl will tell me ‘Ambiguous use of &{_debug} resolved to &_debug’, for a line which contains the following: goto &{_debug};

What exactly might be so ambiguous about this?

---

Relevant code pieces for easier understanding:

package OO::SubModule;

sub new {
  my ($class, $args) = @_;
  my $self = { ( defined $args ? %$args : () ) };
  bless($self, $class);
  
  ## Some boilerplate debug callback that we can override during const
+ruction
  $self->{debug_cb} //= sub { my $self = shift; carp("DEBUG ".join(", 
+", map { defined $_ ? $_ : "undef" } @_)); };
  
  return $self;
}

sub _debug {
  my $self = $_[0];
  goto &{$self->{debug_cb}};
}

## You can say $self->_debug("booya") to do $self->{debug_cb}->("booya
+") without it ending up in the call stack
[download]

## both apps

$oosub = OO::SubModule->new({
  debug_cb => sub {
    my $self = shift;
    my ($str) = @_;
    goto &{_debug};
  },
});

## Any occurrence of $self->_debug("booya") within OO::SubModule reall
+y does _debug("booya") of the main app, this way
## Without getting in the call stack, right?
[download]