string tolower help

I have an irule working as such -

 

when HTTP_REQUEST {

 

set host_used [HTTP::host]

 

set uri_used [HTTP::uri]

 

if { [HTTP::uri] starts_with "/Common/HomeAddress/ABCdef" } {

 

log local0. "[IP::client_addr] sent request $host_used $uri_used"

 

}

 

}

 

When i try using the "string tolower" it errors out.. what am i doing wrong?

 

when HTTP_REQUEST {

 

set host_used [HTTP::host]

 

set uri_used [HTTP::uri]

 

if { [string tolower [HTTP::uri]] starts_with "/Common/HomeAddress/ABCdef" } {

 

log local0. "[IP::client_addr] sent request $host_used $uri_used"

 

}

 

}