How can I remove a query parameter from a URL?

shouldn't HTTP::uri be after foreach loop?

by the way, have you tried it on bigip? it seems okay here.

 configuration

[root@ve11c:Active:In Sync] config  tmsh list ltm rule qux
ltm rule qux {
    when HTTP_REQUEST {
  log local0. "---"
  log local0. "before: [HTTP::uri]"
  if {[HTTP::query] contains "Context_"} {
    set newq ""
    foreach param [split [HTTP::query] "&"] {
      if { !($param starts_with "Context_") } {
        if { $newq eq "" } {
          append newq "?$param"
        } else {
          append newq "&$param"
        }
      }
    }
    if {$newq ne ""} {
      HTTP::uri "[HTTP::path]$newq"
    } else {
      HTTP::uri [HTTP::path]
    }
  }
}
when HTTP_REQUEST priority 1000 {
  log local0. "after: [HTTP::uri]"
}
}

 /var/log/ltm

[root@ve11c:Active:In Sync] config  tail -f /var/log/ltm
May  2 22:15:28 ve11c info tmm[5649]: Rule /Common/qux : ---
May  2 22:15:28 ve11c info tmm[5649]: Rule /Common/qux : before: /test
May  2 22:15:28 ve11c info tmm[5649]: Rule /Common/qux : after: /test
May  2 22:15:33 ve11c info tmm1[5649]: Rule /Common/qux : ---
May  2 22:15:33 ve11c info tmm1[5649]: Rule /Common/qux : before: /test?param1=value1
May  2 22:15:33 ve11c info tmm1[5649]: Rule /Common/qux : after: /test?param1=value1
May  2 22:15:40 ve11c info tmm[5649]: Rule /Common/qux : ---
May  2 22:15:40 ve11c info tmm[5649]: Rule /Common/qux : before: /test?param1=value1&Context_1=123
May  2 22:15:40 ve11c info tmm[5649]: Rule /Common/qux : after: /test?param1=value1
May  2 22:15:45 ve11c info tmm1[5649]: Rule /Common/qux : ---
May  2 22:15:45 ve11c info tmm1[5649]: Rule /Common/qux : before: /test?Context_1=123&param1=value1
May  2 22:15:45 ve11c info tmm1[5649]: Rule /Common/qux : after: /test?param1=value1
May  2 22:15:50 ve11c info tmm[5649]: Rule /Common/qux : ---
May  2 22:15:50 ve11c info tmm[5649]: Rule /Common/qux : before: /test?Context_1=123&param1=value1&Context_2=456&param2=value2
May  2 22:15:50 ve11c info tmm[5649]: Rule /Common/qux : after: /test?param1=value1&param2=value2