[memsom]

That looks a lot like the old Pascal assignment vs equivalence operators. In Pascal (read Delphi) we had '=' for equality and ':=' for assignment. So:

x = 5 <-- a boolean statement, true if x equ 5

x := 5 <-- an assignment of the value 5 to the var x.

TBH, it's only like '=' vs '==' in C like languages. But it's easier to spot errors, as Pascal can never have a valid statement where the two are used in the wrong way.