ELSEIF[xxx]      ELSE with IF                                       Directive

  IF condition1
     statements1
  ELSEIF condition2
     statements2
  ENDIF

    Starts nested conditional assembly block if condition2 is true.

    Several other forms of ELSEIF are supported:
    ELSEIF1, ELSEIF2, ELSEIFB, ELSEIFDEF, ELSEIFDIF, ELSEIFDIFI, ELSEIFE,
    ELSEIFIDN, ELSEIFIDNI, ELSEIFNB, ELSEIFNDEF