Free vs Bound?

How can you tell if a variable identifier is free or bound in a statement?

Foo = proc {$ List Count Length ?Res}


Do they have to be declared and called  to be bound? What about a function? If I set something like R = Foo{ blah blah blah blah} is R bound?

Have you read your CTMCP today?
Simply speaking, when considering the code in a certain scope, an identifier is bound if it is declared within that scope.
If an identifier is used but not declared in the scope, it is free. To make a valid program, it must be declared in an outer scope.
It's not in general a terribly useful thing to think about, except in the context of closures.