Better way to Cleaning UP string variable

How about using scan?

If the variable string is set '9net.tcp://sub.domain.com:12345/abcdefg' or 'sometotherstuff9net.tcp://sub.domain.com:12345/abcdefg/lkjsdflkj/sdfl' etc then try using

scan $string {%*[^/]//%[^:]} fqdn

this results in a new variable $fqdn of 'sub.domain.com'

You can test it out by using the tclsh

% set string "lkasdflkjwe234239net.tcp://sub.domain.com:12345/abcdefg/sdlfkjasf"
lkasdflkjwe234239net.tcp://sub.domain.com:12345/abcdefg/sdlfkjasf
% puts $string
lkasdflkjwe234239net.tcp://sub.domain.com:12345/abcdefg/sdlfkjasf

% scan $string {%*[^/]//%[^:]} fqdn
1
% puts $fqdn
sub.domain.com

Check out this link: https://devcentral.f5.com/articles/irules-101-18revisiting-the-tcl-scan-command

FYI I'm just starting to play with scan so YMMV.

Sheigh