[NEM] ''26 Aug 2006'': [C#] has a nice little construct for automatically
closing a resource once you are finished with it. Here's a Tcl version
of this ''using'' command:

 proc using {varName chan script} {
     upvar 1 $varName var
     set var $chan
     set rc [catch { uplevel 1 $script } result]
     catch { close $chan }
     return -code $rc $result
 }

Which you can then use like:
 using fd [open somefile.txt] { puts [read $fd] }
or
 foreach host $hosts {
     using sock [socket $host $port] { ... do stuff on $host ... }
 }

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[RS] I'm not so happy with the name ''using'': it means other things in other languages (like with packages or namespaces) and does not indicate that it's for channels. Something like [LISP]'s WITH-OPEN-FILE might be clearer to understand :)

[KPV] Actually the [C#] construct is quite useful and not just for
files but for many types of objects which grab some scarce resource.
(Technically, it works with any object which implements the IDispose
interface).

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