The IF statement evaluates a condition.  The condition's truth value
  determines the program action that follows.

  Format -

   IF condition THEN { { stment-1 } ... }
                     { NEXT SENTENCE    }

      [ ELSE { stment-2 } ... [ END-IF ] ]
      [ ELSE NEXT SENTENCE               ]
      [ END-IF                           ]

  Additional Information (explode) :

• stment