> I could list a half dozen languages that don't have multiple implementations (Rust, Java, Scala, C#, PHP, Go) and yet I've never seen anyone raise that as a concern.
That's because you're misinformed! These languages all have multiple implementations (Scala's is just multiple backends), so yeah people don't complain about it.
But hey, why not, I'll give you that one (tbh, I knew including Java on that list was a bit of a stretch).
Care to try with any of the others?
Wanna try to convince me, next, that HHVM qualifies as a reimplementation of PHP despite no one outside of Facebook using it?
But you know what, no, I have a different question: Why does this actually matter? You've positioned this as some sort of objective downside to Perl without explaining why anyone should care. So why don't we start there, rather than my taking your objection as being somehow relevant.
Please, explain to me: Why should I care that Perl (like so many other languages) only has one real implementation?
Because it fosters innovation. Perl isn't innovating as an implementation. Why's that bad? Because you don't get better performance or capabilities, and you're spending more to run it, and spending more to manage it.
> Care to try with any of the others?
For example Mono is a full clean-room implementation of .NET including C#.
> tbh, I knew including Java on that list was a bit of a stretch
That's because you're misinformed! These languages all have multiple implementations (Scala's is just multiple backends), so yeah people don't complain about it.