Strange issue with "matches_regex" and case sensitivity

I'm a relative newbie to iRules, so please don't laugh if this is too simplistic.

 

 

I also have two environments, call them primary and test. I use essentially the same rule (copy/paste) for the two; they differ only by the pools they direct traffic to which is determined by the URI.

 

 

Here's the rule for the primary site:

 

when HTTP_REQUEST {

 

if {[HTTP::uri] matches_regex "/MyURIString" } {

 

pool alt_pool

 

} else {

 

pool main_pool}

 

}

 

 

The rule for the test site:

 

when HTTP_REQUEST {

 

if {[HTTP::uri] matches_regex "/MyURIString" } {

 

pool alttest_pool

 

} else {

 

pool maintest_pool}

 

}

 

 

 

The rule for the primary site works fine, regardless of the case of the URI.

 

ex: https://mysite.com/MyURIString/page.html = OK

 

https://mysite.com/MYURISTRING/page.html = OK

 

https://mysite.com/myuristring/page.html = OK

 

 

In the test site, however, the URL is case-sensitive:

 

ex: https://mytestsite.com/MyURIString/page.html = OK

 

https://mytestsite.com/myuristring/page.html = broken

 

 

Why would one rule require case-sensitivity while the other does not?