gistfile1.txt

MODULE A;
VAR
  p : PROCEDURE
PROCEDURE SetP*(pp:PROCEDURE);
BEGIN
  p:=pp;
END SetP;

PROCEDURE Start*;
BEGIN
  WHILE TRUE DO p END
END Start;
END A.

MODULE B;
IMPORT A;
PROCEDURE P; END P;
BEGIN
  A.SetP(P);
  A.Start;
END B.