GStrings have problems with their various sub parts: the constant strings and the variables interpolated.
With this example:
The first constant string represents "-$ instead of just the minus sign.
The second and third constant are -$ instead of just the minus sign again.
And the last constant is -", instead of just the minus sign, it's going one character too far.
Now on to the variables.
Variable a is okay.
Varible b is actually
and I think it should be just b
And the closure expression is jut right too.