Initial values specified for x, y, ... are evaluated before x, y,... are cleared.

It's from the Details in The reference to Block.

I can't figure out the meaning of this sentence, Could anyone give an example to illustrate it? Thanks a lot!

Initial values specified for x, y, ... are evaluated before x, y,... are cleared.

It's from the Details in The reference to Block. And I can't understand it.

When are the local variables cleared and what's the meaning of "initial values are evaluated"?

Could anyone give an example to illustrate it? Thanks a lot!