Problems with string map and wildcard

what about this?

 configuration

[root@ve11c:Active:In Sync] config  tmsh list ltm rule qux
ltm rule qux {
    when RULE_INIT {
  set static::uri "/MacBlue_SAMTV/GetAttachmentDownloadInfo"
  set static::param_name "encoding"
  set static::param_value "TVOD_"
  set static::param_newvalue "MPEG-4"
}
when HTTP_REQUEST {
  log local0. "before: uri=[HTTP::uri]"
  if { [HTTP::uri] starts_with $static::uri } {
    set value [URI::query [HTTP::uri] $static::param_name]
    if { $value starts_with $static::param_value } {
      HTTP::query [string map [list $static::param_name=$value $static::param_name=$static::param_newvalue] [HTTP::query]]
    }
  }
}
when HTTP_REQUEST priority 1000 {
  log local0. "after: uri=[HTTP::uri]"
}
}

 /var/log/ltm

May 26 11:42:15 ve11c info tmm[32414]: Rule /Common/qux : before: uri=/something
May 26 11:42:15 ve11c info tmm[32414]: Rule /Common/qux : after: uri=/something

May 26 11:42:32 ve11c info tmm1[32414]: Rule /Common/qux : before: uri=/MacBlue_SAMTV/GetAttachmentDownloadInfo?something=1234
May 26 11:42:32 ve11c info tmm1[32414]: Rule /Common/qux : after: uri=/MacBlue_SAMTV/GetAttachmentDownloadInfo?something=1234

May 26 11:42:42 ve11c info tmm[32414]: Rule /Common/qux : before: uri=/MacBlue_SAMTV/GetAttachmentDownloadInfo?encoding=TVOD_123_456&test=789
May 26 11:42:42 ve11c info tmm[32414]: Rule /Common/qux : after: uri=/MacBlue_SAMTV/GetAttachmentDownloadInfo?encoding=MPEG-4&test=789

May 26 11:42:59 ve11c info tmm1[32414]: Rule /Common/qux : before: uri=/MacBlue_SAMTV/GetAttachmentDownloadInfo?prefix=abc&encoding=TVOD_123_456&test=789
May 26 11:42:59 ve11c info tmm1[32414]: Rule /Common/qux : after: uri=/MacBlue_SAMTV/GetAttachmentDownloadInfo?prefix=abc&encoding=MPEG-4&test=789