I tried running that little embedded Kotlin example using jAlbum's scripting console and received the following error:
in inline evaluation of:
e.eval("val x = 3");'' at line number 1
Moreover, the following debug print is also generated:
81084 [AWT-EventQueue-0] INFO kc - Compiling '/var/folders/hc/55gr2vw145b0m7cpllskd0ph0000gn/T/kc_evl4159402832513912920.kts'...
This shows that Kotlin writes stuff to the file system for each script execution. Not good.