[int_19h]

This has been the usual way to implement interpreted languages for decades; Perl isn't special in that regard. JIT generally refers to generation and execution of native code specifically.

[jandrese]

I'm pretty sure bash still interprets line by line because you can mess up a script by editing it while it is executing.

[int_19h]

bash (and other shells) are special in that regard, because they use textual substitution so heavily - to pass arguments etc.

But Python, Ruby etc all compile to bytecode, and have always done so as far as I can remember.