Description:
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This isn't really a bug, but I think it would be great to have a control structure that has temporary execution parameters.  Consider it an execution space similar to a while or switch, etc.

The reason I could use it in this particular instance is for security reasons.  For certain code, I need to elevate a logged in user's "status" to temporarily give them super user permissions.  Basically I temporarily convert the user, run the code, then convert them back.

convert_user();
execute_code_here();
convert_user_back();

This works great, of course, but if I have to do this 300 times, there is a decent chance that I would forget to convert_user_back();, causing a security hole (the user would then be logged in as a super user).

It would be great if I could do something like

execspace conversion_space ($params[]) {
     function start () {
          convert_user();
    }
    function stop  () {
          convert_user_back();
   }
}

Then in my actual code, I would do:

conversion_space {  // start function executes here
      // execute some code
} // stop function executes here

This way, it is grammatically impossible to implement the structure without closing it.

I think this would be a powerful control structure for the language.  Perhaps there is an equally useful solution that I am unaware of, but if not, I think implementing it is worth consideration (and if there is, I would certainly appreciate the enlightenment!)