[TheFluff]

I deleted the post because I thought the discussion had already covered what I was talking about but here's the relevant part again:

Avisynth has four types of expressions:
1) explicit returns ("return <expression>")
2) explicit assignments ("variable = <expression>")
3) implicit assignments to last (all expressions that aren't one of the two first types and evaluate to a clip)
4) other expressions where the return value is thrown away (everything else)

When the last expression in a block (either a function or a script) is not an explicit return (type 1 above), Avisynth will evaluate the expression and implicitly return the value it evaluates to, regardless of what the type of that value is (clip, int, string, undefined, whatever). The quirky thing here is that while expressions of type 3 and 4 above return the value of the expression, an explicit assignment returns an undefined value. I think this is a lazy fix to make sure an explicit assignment of a clip to an arbitrary variable doesn't overwrite last, which I suspect would happen if the assignment returned the assigned value like every other assignment operator on the planet does. The inconsistency is that an explicit assignment returns undefined while an implicit assignment to last returns the assigned value.

What TurboPascal7 proposed to change is simply the implicit return mechanism: if you attempt to implicitly return an explicit assignment expression, last should be returned instead of the undefined value, if last is defined at that point. The problem with this is that there's nothing about the scripting language that forces you to use last, and thus there's really nothing that says that at the end of a block the contents of last would be a better or more correct value to return than any other arbitrary value. I can accept an operator returning an undefined value, even if I think that's ugly, but having an operator return a defined, arbitrary value that may be completely unrelated to any of its operands is beyond ugly.

What I think you should do is promote the assignment operator to full citizen status like all of Avisynth's other operators, give it a place in the precedence table and make it return the assigned value like assignment operators in basically every other language do. Then fix the script parser so this doesn't overwrite last when the assigned value is a clip. This will probably break things though.