58. While...do structure
    ~~~~~~~~~~~~~~~~~~~~
You may have missed the presence of a WHILE-DO or WHILE-ENDWHILE in BBC Basic
(it's in version5 as per the Arc). Eg.

   WHILE X%<100 DO X%=X%+1:A%=A%*B%
or
   WHILE X%<100:X%=X%+1:A%=A%*B%:ENDWHILE (as on BBC BASIC V)

REPEAT-UNTIL and FOR-NEXT loops have a disadvantage compared to WHILE-DO or
WHILE-ENDWHILE loops in that they always execute at least once, whether they
need to or not. In the examples above, the loop would not execute at all if
X% was >=100.

Well, you can imitate WHILE-DO or WHILE-ENDWHILE with the following:

  REPEAT IF X%<100 THEN X%=X%+1:A%=A%*B%:UNTIL FALSE ELSE UNTIL TRUE

It may not look very elegant, but it avoids GOTOs, so that makes it
structured in my book! (Source ... Beebug).