A does method sounds like a boolean to me. I'd look for it to return true if and only if the object can do all the listed methods. Also, your error return will not occur if $proto is not a reference.

sub does {
    my ($proto, @methods) = @_;
    return if !ref $proto || !blessed $proto; # DeMorgan
    my @coderefs = map {$proto->can($_) || ()} @methods;
    return @coderefs == @methods;
}
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