ProxyPass Removing Trailing Slash in Host?

I ended up creating a quick iRule to simply select another pool, rather than using ProxyPass. ProxyPass was chosen because it was already implemented for other solutions.

I'd still be curious as to why the trailing slashes weren't handled correctly on this one.

Here's the iRule I ended up using

when HTTP_REQUEST {
    if { [string tolower [HTTP::host]] equals "site1.mainsite.domain.com" } {
        pool site1_1111_dev
    }
}