| program p | |
| call ctn1 | |
| call ctn2 | |
| call ext1 | |
| call ext2 | |
| contains | |
| subroutine ctn1 | |
| call ctn2 | |
| call ext1 | |
| call ext2 | |
| end subroutine | |
| subroutine ctn2 | |
| call ctn1 | |
| call ext1 | |
| call ext2 | |
| end subroutine | |
| end program p | |
| subroutine ext1 | |
| call ext2 | |
| end subroutine ext1 | |
| subroutine ext2 | |
| call ext1 | |
| end subroutine ext2 |