package My::Interface::VersionBased;

sub new {
    if ($some_condition) {
        return My::Interface::VersionBased::ForCondition1->new(@_);
    }
    elsif ($some_other_condition) {
        require My::External::Interface;
        return My::External::Interface->new( @_ );
    }
    else {
        die "Unable to find a proper interface";
    }
}