Built-in type var(_)

[Tony Hannan]

Hello,

I was writing an MVar module (a' la Haskell) and defining the type

    -type var(A) :: {var, pid(), A}.
    % initial value kept in reference for type only, current value held in
process

But the compiler complained that

    "type var(_) is a builtin type; it cannot be redefined"

I don't see this built-in var mentioned in any of the documentation and
Google didn't find it either. So where is this var type defined and can I
use it instead of creating my own var type.

Thanks,
Tony