Fix onoff

It seems the same problem as on #292, but the code was moved to a new location to fix other problems in itentifier_led_stmt and doing that undid the fix.  (Or, more accurately, when I re-implemented it in the new method, I did it the wrong way so it caused the same sort of problem in parallel for a slightly different reason - the problem being that the value didn't parse as a settable identifier, so it pushed "SAS" on the stack rather than "$SAS".)