[TJE]
This little mismatch has bitten me in code, so I thought I'd shed a little more light on the matter for those who may not have picked up on it from the documentation...

The ranges placed in a switch statement's "-indexvar" target are inclusive of the character AFTER the match.  This differs from the behavior of [regexp]'s "-indices" option, which is exclusive of the same character.

Here's a simple example:

  % set line {foo bar}
  foo bar
  % regexp -inline -indices {foo} $line
  {0 2}
  % switch -regexp -indexvar index -- $line {foo} {set index}
  {0 3}

As you can see, regexp reports the actual match (character '0' through '2' matches "foo"), whereas switch reports the match PLUS the character after (character '0' through '3' matches "foo ").

Don't get bitten!

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Curiously, [TIP]#75 [http://tip.tcl.tk/75] (which seems to be the only one that specifies this feature) states (emphasis added):
    :   the new option `-indexvar` will also be provided which will name a variable into which a list of match indices (each a two item list of values ''in the same way that [[regexp -indices]]'' computes) will be placed
This rather suggests that the stated mismatch is a bug...

'''[DGP]''' Please have a look at the documentation for [regexp] and [switch].
[http://www.tcl.tk/man/tcl8.5/TclCmd/regexp.htm] [http://www.tcl.tk/man/tcl8.5/TclCmd/switch.htm].
Appears to me the [switch] '''-indexvar''' option is operating exactly as
it is documented to do.  ''As a meta-comment, I think the Tracker is a much better
place to resolve question like this than the wiki.''

Is it significant that tcl/tests/switch.test does, in fact, have tests
for use of -indexvar (in conjuntion with -matchvar) and the tests appear
to be passing? Either the tests aren't testing indexvar the way one would
think, the test writer ''cooked'' the tests so they would pass even
though not producing the real expected results, or the code is doing the
right thing, but has, perhaps, the wrong docs. See tcl/generic/tclCmdM.c,
function Tcl_SwitchObjCmd for the code which provides the [switch] functionality.

======
set string "The quick brown fox jumped over the lazy dogs."

set matches {}
set indexes {}

switch -regexp -matchvar matches -indexvar indexes -- $string {
  ^(.*)u([a-z]+)(.*)(o[a-z]+)(.*)\.  {
        puts "Found"
        puts " matches = .${matches}."
        puts " indexes = .${indexes}."
   }
  default {
        puts "string = $string"
  }


}

Found
 matches = .{The quick brown fox jumped over the lazy dogs.} {The quick brown fox j} mped { over the lazy d} ogs {}.
 indexes = .{0 46} {0 21} {22 26} {26 42} {42 45} {45 45}.
======

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