A better way

You could use a switch statement on the string length of $port_info to avoid using a regex. The string length command is more efficient than the regex comparison.

...
switch [string length $port_info] {
   1 { pool $poolname400$portinfo }
   2 { pool $poolname40$portinfo }
   3 { pool $poolname4$portinfo } 
}

If you do stick with the regex, I think you'll need to adjust the comparisons. [10-99] would mean match a single character that's either 1, 0 through 9, or 9. Likewise [100-254] would match a single character that's either 1, 0, 0 through 2, 5 or 4.

Else, if you wanted to avoid using a rule altogether, you might be able to use the least connections load balancing method to ensure the load is distributed evenly, with source address persistence to ensure clients are sent to the same node. You'd need to add all of the nodes from the current 254 pools into one pool though.

Aaron