{
        no strict 'refs';
        no warnings 'redefine';
 
        my $mock = $self;
        weaken $mock;
 
        *$sub = sub {
 
            @{ $mock->{called_with} } = @_;
            ++$mock->{called_count};
 
            if ($mock->{side_effect}) {
                if (wantarray){
                    my @effect = $mock->{side_effect}->(@_);
                    return @effect if @effect;
                }
                else {
                    my $effect = $mock->{side_effect}->(@_);
                    return $effect if defined $effect;
                }
            }
 
            return if ! defined $mock->{return};
 
            if ($mock->{return}[0] && $mock->{return}[0] eq 'params'){
                return ! wantarray ? $_[0] : @_;
            }
            else {
                return ! wantarray && @{ $mock->{return} } == 1
                    ? $mock->{return}[0]
                    : @{ $mock->{return} };
            }
        };
    }