Java for example runs arbitrary code when a class is loaded (static {} blocks).
Windows has DllMain, which lets you run code at load of a shared lib and similar things are possible on Linux, using the -init linker flag and friends.
Finally, Haskell has features that allow you to load, compile and run Haskell (through the GHCMonad, if installed), which allows precisely for those shenanigans.
All those lack the habit that the OP is describing (and which broke for him): the use runtime introspection during development time (possibly in a REPL), but that's another pair of shoes.
Windows has DllMain, which lets you run code at load of a shared lib and similar things are possible on Linux, using the -init linker flag and friends.
Finally, Haskell has features that allow you to load, compile and run Haskell (through the GHCMonad, if installed), which allows precisely for those shenanigans.
All those lack the habit that the OP is describing (and which broke for him): the use runtime introspection during development time (possibly in a REPL), but that's another pair of shoes.