Fix typo in example

[aphillips]

Fixes #857

Thanks to @mvilks for noticing.

[mihnita]

Approved.

But to nitpick a bit, I would go with something like

.local $foo={|bar|} {{{$foo :func}}}

or

.local $variable={|value|} {{{$variable :func}}}

As it is, var is a keyword in several programming languages, so it might lead people to think there is something special about it here.
And the fact that the name of the variable and the value are the same might also throw off some people.