It was the same as in many FORTRAN IV dialects and also in ALGOL and in many other early languages, but in FORTRAN that was not a standard language feature, even if many compilers implemented it as a language extension.
I was responding to "completely absent in all modern languages". Alternate return has been in the standard since '77, and Fortran 2018 seems modern enough.
In which FORTRAN IV dialects was it the same as in PL/I?
I should have said that alternate return is obsolescent in recent Fortran, and I don't remember ever feeling the need to use it, at least for error-handling.