'''`[http://www.tcl.tk/man/tcl/TclCmd/unset.htm%|%unset]`''', a [Tcl Commands%|%built-in] [Tcl] [command], removes one or more variables.


** Synopsis **

    :   '''unset''' ?'''-nocomplain'''? ''varName'' ?''varName ...''?



** Documentation **

   [http://www.tcl.tk/man/tcl/TclCmd/unset.htm%|%official reference]:   



** Description **

It is an error for the variables to not already exist, the name to be illegal,
etc. This error can be suppressed with the '''`-nocomplain`''' option.

A [trace] on the variable can resurrect it.

[DKF]: In 8.6, `[unset]` is bytecode compiled. (And don't use `catch
{unset foo}`; the operationally-equivalent `unset -nocomplain foo`
generates much better bytecode.)

----

In retrospect, `unset` should have been designed so that it was not an error to
In retrospect, `unset` should have been designed so that it was not an error to
`unset` a variable that didn't exist, in which case `-nocomplain` would not
have been necessary. 
Unsetting a variable will remove all the [trace]s on it.  If there are any `variable unset` traces, they will first be called.
Proc-local variables are implicitly unset when the proc returns.  By using an unset trace, we can do sneaky things:
======
** Misc **

[Erik Leunissen] on [comp.lang.tcl] 2002-10:

===
    Well, I've been bitten by this one on a *regular* basis, but not on a
    *frequent* basis. So infrequently, that I tend to forget about the issue, and
    once it happens again, it takes me by surprise and I need hours to find the
    cause of evil, which I'll explain:
    
    The following happens when you bind a variable to an entry widget 
    through the `-textvariable` option and subsequently issue [[unset 
    textvariable] :
    
       1. the textvariable may become unset for a fraction of a millisecond, I'm not sure. Perhaps somebody else can elaborate on this ...
       2. the textvariable binding will immediately reassign the value of the contents of the entry widget to the textvariable. (If it has been unset for a short moment, it is recreated)
    
    So what's the recipe then?
    
       1. release the binding to the entry widget by:
       ** doing [[.entry -textvariable {}], or
       ** destroying the widget entirely
       2. unset the variable: [[unset textvariable]
       3. try to remember this issue (better than I do) when it takes you by surprise the next time.

For the coming releases of Tcl (still in CVS), you can also set an unset trace
on the textvariable, and let the trace handler do the above step one and/or
two. For current releases this will not yet work because of a (recently fixed)
bug.
===
proc test {n cmd} {


'''`[http://www.tcl.tk/man/tcl/TclCmd/unset.htm%|%unset]`''', a [Tcl