Here is my haproxy fornt-end config:

#WORKING
frontend osconsoleproxy
        bind 10.0.0.58:6080
        option tcplog

        acl url_path path /vnc_auto.html
        acl param_token urlp_reg(token) [0-9a-fA-F]+-[0-9a-fA-F]+-[0-9a-fA-F]+-[0-9a-fA-F]+-[0-9a-fA-F]{1,36}$
        acl param_keykey1 urlp(key) console1
        acl param_keykey3 urlp(key) console3

        default_backend control1-backend

        tcp-request inspect-delay 2s
        tcp-request content accept if param_keykey1

#NOT-WORKING
frontend osconsoleproxy
        bind 10.0.0.58:6080
        option tcplog

        acl url_path path /vnc_auto.html
        acl param_token urlp_reg(token) [0-9a-fA-F]+-[0-9a-fA-F]+-[0-9a-fA-F]+-[0-9a-fA-F]+-[0-9a-fA-F]{1,36}$
        acl param_keykey1 urlp(key) console1
        acl param_keykey3 urlp(key) console3

        use_backend control1-backend if param_keykey1

        tcp-request inspect-delay 2s
        tcp-request content accept if param_keykey1