I found some time to write an interactive test environment for crystal functions.
It has a CLI which can be used to manage vars and start functions and procs stored in a hash table.
While it is a sort of text interpreter its not that slow:
Example test script:
Welcome to tree
Loaded: counter2.txt Number of lines: 11
reached end of file
# ~ 5 sec with scripter now counter = 0 p counter while counter < 1000000 counter+= 1 #p counter end p counter now