Following iRule not working in my setup please correct mistake if found

Try this:

when HTTP_REQUEST { 

      if {[string tolower [HTTP::host]] eq "mfcomb.birlasunlife.com"}{

              switch [string tolower [HTTP::uri]] {

                "/media*" -
                "/mediaupload*" -
                "/webchat*" -
                "/webtrak*" {

                       pool Talisma_MF_Webchat
                }
                default {
                        pool UAT-VS_pool
                }
              }
        }
    }

or alternativly your version/way

when HTTP_REQUEST { 

    if {[string tolower [HTTP::host]] equals "mfcomb.birlasunlife.com"}{ 

        if { ([string tolower [HTTP::uri]] starts_with "/media") or ([string tolower [HTTP::uri]] starts_with "/mediaupload") or ([string tolower [HTTP::uri]] starts_with "/webchat") or ([string tolower [HTTP::uri]] starts_with "/webtrak") }{ 

                  pool Talisma_MF_Webchat

           } else { 

             pool UAT-VS_pool 
        } 
   }
}