Required help for irule on single url

Just one approach - I'd create 3 pools;-

pl_xyz_http members {2.2.2.2:80 2.2.2.3:80}
pl_def_http members {2.2.2.3:80 2.2.2.4:80}
pl_ghi_http members {2.2.2.4:80}

Then on your VIP apply round-robin and oneconnect profile and the following iRule;-

when HTTP_REQUEST {
    set path_seg1 [lindex [split [HTTP::path] / ] 1 ]
    switch $path_seg1 {
        "xyz" -
        "abc" -
        "ghi" {
             Rewrite Host header
            HTTP::header replace Host "${path_seg1}.com"
             Rewrite path
            HTTP::path "/"
            pool "pl_{$path_seg1}_http"
        }
        default {
             Will be sent to default pool attached to virtual
        }
    }
}

There are obviously many ways to approach this though