print_hex Subroutine

   subroutine print_hex(str)
      use :: iso_fortran_env
      implicit none
      character(*), intent(in) :: str

      character(5) :: buf
      character(:), allocatable :: form
      integer :: j

      write(buf,'(i0)') len(str)
      form = trim(adjustl(buf))
      write(output_unit, '(a, i7, a,'//trim(form)//'z2)')  'len = ', len(str),'; hex=', [(str(j:j), j=1, len(str))]
      write(output_unit, '(a)') "+----------------------------------------------+"

   end subroutine print_hex