We were forced to make one change to Ratfor90 because of new things in Fortran90. Ratfor77 allows & and | for the logical operators && and ||. While attractive, it is not part of the C family of languages and we had to drop it because Fortran90 adopts & for line continuation.
Because we are not compiler writers, we dropped a rarely used feature of Ratfor77 that was not easy for us to implement and is ugly anyway: Ratfor77 recognizes break 2 which escapes from {{ }}.
Changing all the code that generated illustrations for four textbooks (of various ages) also turned up a few more issues: Fortran90 uses the words scale and matmul as intrinsics. Old Fortran77 programs using those words as variable names must be changed. Ratfor77 unwisely allowed variables of intrinsic (undeclared) types. We no longer allow this. Ratfor90 forces implicit none.
New features in Ratfor90 are bracketed type, subroutine, function, and module procedures. In some ways this a further step towards the C, C++, Java model. It makes complicated modules, subroutines inside subroutines, and other advanced features of Fortran90 easier to interpret. Ratfor90 has better error messages than Ratfor77. Besides the use of stderr, a new file (ratfor_problem) marks the difficulty.