[TCLCORE] handling loops interruption within a 'try'

[Massimo M. <mas...@ri...>]

I apologize for (ab)using this mailing list to ask a question that maybe 
has a trivial answer.

I just can't have the 'on break' clause be triggered in a loop 
controlled by a 'try' construct

try {
     while {[some_expensive_query]} {

         # ....

         if {[some_intervening_condition]} {
             return -code break -level 0
         }

         # ....
     }
} on break {} {
     puts " ---- break ----"
     puts "Loop interrupted by break"
} on ok {} {
     puts "Loop completed normally"
} finally {
     puts "done"
}

and you have a normal termination even though the loop was interrupted 
prematurely by [some_intervening_condition]

I can get what I want by raising an exception with 'throw' and then 
using the trap clause which allows extra control over the cause of the 
exception (-errorcode receives no special treatment unless the option 
-code error is passed) but what is the purpose of the 'on break' clause 
if it's not handling a break?

  -- Massimo