Help with Scan or String first last and multiple/last occurence

This is a derivative of what Patrik suggested that I came up with as a result of also in some cases needing to match the second to last field of dash delimiters in a hostname

I think this is the best way to do this with lindex because it removed the dependency on the number of periods in the original hostname. Now the only dependency is that the target part of the hostname containing dashes is on the leftmost side of the hostname

So to find the last field of a dash delimited string in an HTTP::host

set httphost "test-tools-config.acme.com"
set a [string tolower [lindex [split [lindex [split [getfield $httphost ":" 1] "."] 0] "-"] end]]
 a = config

And to find the second (or N) to last field of a dash delimited string in HTTP::host

set httphost "test-tools-config.acme.com"
set b [string tolower [lindex [split [lindex [split [getfield $httphost ":" 1] "."] 0] "-"] end-1]]
 b = tools

The only reason that lindex can do this with variable field delimiters where scan, string, etc fail, is that it allows the "end" and "end-N" operator

Honestly, I think a built in function is needed in irules similar to "getfield", but would be "reverse" to reverse a string. I believe native TCL has a "string reverse", but it is not enabled for some reason in irules : (. Perhaps it doesnt gain mutch anywa since with lindex I must do two splits and two lindex's and one getfield to accomplish this. With a reverse function it would be just less lindex's and more reverse's The goal was really to use SCAN, but unless irules is going to allow a custom flag in SCAN similar to "end" and "end-N" then I guess it just all boils down to string/array functions