...
sub ObjectToString {
    my $name = shift;
    return sub {
        my $s = $name . $self->getParametersAndValues();
        return $s;
    }
}
...
package Fu;
sub toString = ObjectToString("Fu");
...
package Bar;
sub toString = ObjectToString("Bar");
...
package Baz;
sub toString = ObjectToString("Baz");
...

##</code><code>##

my ($foo, $bar, $baz);

$foo = Fu->new();
# do stuff with foo...
print $foo->toString();

$bar = Bar->new();
# do stuff with bar...
print $bar->toString();
...