Richard Suchenwirth 2005-04-08 - What happens when a [proc calls itself. Popular in functional programming. In Tcl, we're a bit handicapped by the [interp recursionlimit] which is at ~380 on Windows, even if set higher.
Here's an example for a recursive integer range generator, so that [iota1 5] == {1 2 3 4 5} :
proc iota1 n {expr {$n == 1? 1: [concat [iota1 [- $n 1]] $n]}}