  Far from the latest innovations in software development, many organizations
still rely on old code written in "obsolete" programming languages. Because
this source code is old and proven it often contributes significantly to the
continuing success of these organizations. Yet to keep the applications
relevant and running in an evolving environment, they sometimes need to be
updated or migrated to new languages or new platforms. One difficulty of
working with these "veteran languages" is being able to parse the source code
to build a representation of it. Parsing can also allow modern software
development tools and IDEs to offer better support to these veteran languages.
We initiated a project between our group and the Framatome company to help
migrate old Fortran-77 with proprietary extensions (called Esope) into more
modern Fortran. In this paper, we explain how we parsed the Esope language with
a combination of island grammar and regular parser to build an abstract syntax
tree of the code.
