Perl's decline was cultural

I still remember spending time with my coworkers on bench outside of building trying to figure out #@$%$^&$%@something = []sd[dsd]@$#!&lala lines written by previous developers

The original intent was you could see var types with them - $scalar, @array, %hash.

They immediately broke this by deciding the sigil would apply to the value /extracted/ from the data structure. So you declared array @foo but accessed an element as $foo[1]. What? There’s a logic there but already you’re violating many people’s expectations so why even have them. The sigils are now confusing many people instead of clarifying anything.

The sigil idea then /completely/ failed when they introduced references and “complex data structures” (nesting arrays within arrays like every other language - in Perl this was a special thing because they had been flattening lists by default so no way to put one inside another).

So now to get at a hash in a hash you used not % but $ since a reference is a scalar. $hash1->$hash2->{“key”}. Versus $hash3{“key”} for a simple hash. Just awful noisy syntax. Due to poor language design up front.