Many subtle differences between implementations! There is the ANS standard, but usually one encounters a mix&match of the personal taste. Try porting code, and likely be surprised. This aside...

Get your guns ready, dare to forget PAUSE in a task being in a cooperative multitasker.

Whereas Forth definitions, on a stack based language, are mostly reentrant, the use of mostly global variables in many strategically important places is not. Take care if you use interrupts.