How to manage part of a STRING?

[LukeBord1]

In standard Basic, we have this example correctly working:

Code:

10 LET a$="123456789012345678901234567890xy"
20 PRINT AT 0,0; a$
30 IF INKEY$="0" THEN LET a$=a$(32) + a$(1 TO 31)
40 GOTO 20

...but it doesn't seem to work in ZXB:

Code:

DIM test AS STRING
test="123456789012345678901234567890xy"
mainloop:
PRINT AT 0,0; test
IF INKEY="0" THEN
test=test(32) + test(1 TO 31)
END IF
GOTO mainloop

Thoughts?