-- https://docs.oracle.com/en/database/oracle/oracle-database/23/lnpls/plsql-subprograms.html
DECLARE
  -- Declare proc1 (forward declaration):
  PROCEDURE proc1(number1 NUMBER);

  -- Declare and define proc2:
  PROCEDURE proc2(number2 NUMBER) IS
  BEGIN
    proc1(number2);
  END;

  -- Define proc 1:
  PROCEDURE proc1(number1 NUMBER) IS
  BEGIN
    proc2 (number1);
  END;

BEGIN
  NULL;
END;
/