Perhaps this could be a job for use overload. Use byVersion as the comparison operator, and create a simple function for the stringification operator. If your constructor simply blesses a reference to the string, the stringification would be something as simple as:

my to_string{
    my $s=shift;
    return $$s;
}
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I've just done something similiar with the versions names we use for our software releases. They are a bit weirder, but it works great...

GoldClaw