[cthor]

There are no programs that will fully transpile Perl to not-Perl, because that would require parsing Perl.

A code converter that kindof-sortof-but-not-really transpiles (like Python's 2to3) would require a lot of debugging of ugly machine generated source code. Who wants to do that? Would probably be even harder than a full rewrite. (How many Python libraries were actually ported using 2to3?) Similar for using any translation an LLM might spit out.

So yes, by hand. And it's not obvious if a full rewrite of a complex library would be easier than porting its runtime to WASM, especially when said runtime has been ported to countless other systems already.