package MyClass;

sub new {
    my ($class, @parameters) = @_;
    return bless {params => \@parameters}, $class;
}

sub fetch {
    my $self = 
    return $self->{'cache'} //= do {
        sleep 1;
        warn "cache miss. Generating value...\n";
        _gen_value($self->{'params'}) #; Generate the expensive value and store it in the cache.
    };
}