if "www.abc.com/1" then goes to first pool member.
"www.abc.com/2" then goes to second pool member.
you can use HTTP::uri command to check uri (e.g. /1, /2) and then send traffic to specific pool member using node or pool (pool ... member ...) command.
HTTP::uri
https://devcentral.f5.com/wiki/irules.http__uri.ashx
node
https://devcentral.f5.com/wiki/iRules.node.ashx
pool
https://devcentral.f5.com/wiki/iRules.pool.ashx
if "www.abc.com" then rewrites to "www.abc.com/test" ---> server pool A
if "www.abc.com/test1" then ---> server pool B
if "www.abc.com/test2" then ---> server pool C
HTTP::uri command is also used to rewrite uri (e.g. / to /test).