`letstx` fails inside loops

Created by: amatiasq

Trying to implement somethink like this I get the error Cannot read property '0' of undefined.

It may be generated by caused because letstx is trapped inside the while block and can't access the rest of the syntax. If I remove the while block it works.

I don't know how hard this is to implement but I think letstx should work in cases like this one for coherency.

With help from @disnet we've generated a $($token) ... bucle from the case macro but it's a little bit confusing: http://bit.ly/1d1yWU8