use Test::More;

package Foo {
    sub new     { bless { }, shift };

    sub method  {
        my ($self, $arg) = @_;
        # Network operation followed by internal processing, but
        # for the sake of example, say we've already done all
        # that and it's in $arg. (Normally method takes no args,
        # and is non-idempotent):

        wantarray ? (_special_to_string($arg), $arg)
                  :  _special_to_string($arg);
    }

    sub _special_to_string {
        # Really requires 100-odd lines of transformation code,
        # split among several other internal subs, but for now:
        lc(shift);
    }
}

my $arg = 'Really Special';

my $foo = Foo->new;
is scalar $foo->method($arg), lc($arg), 'explicit scalar context';
my $string = $foo->method($arg);
is $string, lc($arg), 'scalar assignment';

my ($plain, $special) = $foo->method($arg);
is_deeply [ $foo->method($arg) ], [ lc($arg), $arg ], 'list';

__END__
ok 1 - explicit scalar context
ok 2 - scalar assignment
ok 3 - list