Begin  
  L1: if B1 then goto L2;
      S1;
      if B2 then goto L2;
      S2;
      goto L1;
  L2: S3;
End

/* Rewritten - equivalent */
Begin  
  L1: if B1 
      then goto L2;
      else begin
             S1;
             if B2 
             then goto L2;
             else begin
                    S2;
                    goto L1;
                  end
           end
  L2: S3;
End

(letrec ((L1 (lambda ()
                (if B1 
                    (L2)
                    (begin
                      S1
                      (if B2 
                         (L2)
                         (begin 
                            S2
                            (L1)))))))
         (L2 (lambda ()
                S3)))
  (L1))

#include 
#define DUMMY 0

int main(void) {
  int B1 = 1, B2 = 1;
  int S1 = DUMMY, S2 = DUMMY, S3 = DUMMY;
  
  L1: if (B1) goto L2;
      S1;
      if (B2) goto L2;
      S2;
      goto L1;
  L2: S3;
}