Question: assignment of a multi varibled variable

In Maple we can assign single named variables to values.  I was just wondering if it would be worthwhile if Maple could be set up to work with a multivariable assignment.  Not sure if my wording is understandable but hopefully someone can understand my point, or deter me from even thinking that way. 

Would it ever help in calculations in Maple if we were to make an assignment something like this :

v²:= a² + b²

or

a * b := 3*x + 5*y²

Haven't looked into it too hard, I'd like to know if there might be a situation where this type of assignment would be helpful.  I mean, does it make sense to do this kind of thing.  I wonder if there is a situation where this type of thing is useful, or maybe it's just impossible to work right anyway.  Maybe it's already been tried?  Thoughts?