|No such thing as a small change|
"Seem to" dominate? The very meaning of the name of Perl suggests it would be predominately focused on sequential text files.
That said, and DBM::Deep already mentioned, if you want to spin your own module to support what we in the dinosaur days would have called Fixed-Length Random Access File processes, you could look into the following features of Perl:
Input and output functions:
Modern data processing (is that an oxymoron?) thinks more in terms of XML and DB for re-usable, rewriteable data; but if you must play in the old fashioned fixed-length random-access file space, the above tools will readily permit migration of your old C code where you last reinvented that wheel to Perl where you seem fixated on this somewhat dated approach to data storage.
All that having been said, I myself could not resist the urge to port my old FLRAF routines to Perl when I first got here. I never bothered to write a module I would dare to put in front of other software engineers, however, since I knew going into the effort it was an exercise to produce a tool I was unlikely to ever need.
DBI/SQLite has been a good friend:
Updated to computerize DBM::Deep