Internal (nested) procedure support

[ppenzin]

From F95 standard (this can be inside of a main program or a subprogram):

R210    internal-subprogram-part is contains-stmt
                                      internal-subprogram
                                      [internal-subprogram] ...

Also see Intel Developer Zone example. Basically, you can specify a nested procedure inside another procedure or main program using CONTAINS. A toy example:

$ cat internal.f90 
subroutine s(x)
  integer x
  call s2(x)
  contains
    subroutine s2(y)
      integer y
    end subroutine
end subroutine
$ gfortran -fsyntax-only internal.f90
$ fort -fsyntax-only internal.f90
internal.f90:4:11: error: expected '='
  contains
          ^
internal.f90:5:16: error: expected '='
    subroutine s2(y)
               ^
internal.f90:6:15: error: expected '='
      integer y
              ^
internal.f90:8:1: error: expected 'end program'
end subroutine
^
<unknown>:0: note: to match this 'program'
$