Michael,
I think HEX() has never been a 4gl function, it's an Informix SQL function:
main
define h varchar(20)
database test1
select hex(123) into h from systables where tabid = 1
display h
end main
Following line does not compile with Informix 4gl 7.32:
let h = hex(123)
Are you sure that this function was not implemented as a C extension by yourself?
A list of de-supported functions can be found here:
https://4js.com/techdocs/genero/fgl/devel/DocRoot/User/BuiltInFunctions.html#DESUPLISTSeb