It is straightforward to call a block such as the following

call { private _a = 0; _a = 1 }

However, the return value of such a block is not nil, but undefined. For example, executing the following

typeName call { private _a = 0; _a = 1 };

Produces an error at the typeName operator:

Error Generic error in expression

I'd like the return value of such a block be either nil or (probably more usefully) the assigned value at the end of the block. Each of the following statements produces no errors

typeName call { nil };
typeName call {};
typeName call { 1 }

The ideal would be that executing the following code

typeName call { private _a = 0; _a = 1 };

would produce the result of "SCALAR".

Note that the code

typeName call { private _a = 0 };

would produce the same result. It doesn't make any sense to create a private variable as the last statement of a block, but there is no harm in having the assigned value pass through to establish the return value of the code block.