I'm 1000% on board with replacing oid constants with symbolic names
that get substituted programmatically.
However I wonder why we're bothering inventing a new syntax that
doesn't actually do much more than present static tabular data. If
things like magic proname->prosrc behaviour are not valuable then
we're not getting much out of this perl-friendly syntax that a simpler
more standard format wouldn't get us.
So just as a straw man proposal.... What if we just replaced the data
file with a csv file that could be maintained in a spreadsheet. It
could easily be parsed by perl and we could even have perl scripts
that load the records into memory and modify them. You could even
imagine writing a postgres script that loaded the csv file into a
temporary table, did complex SQL updates or other DML, then wrote it
back out to a csv file.