Irule Match

I'll include the code again for readability (with additional comments):

switch -glob [HTTP::uri] { 
    "/foo*" { 
         this will match on any string that starts with "/foo" 
    }
    "bar" { 
         this will match on a string that equals "bar". The -glob operator allows you to include regex-like wildcards in the expressions. And since you didn't specify any here, the match is explicit.
    }
    "/foobar[a-zA-Z]" { 
         This will match with any string that starts with "/foobar" followed by any case character from a-z. Except that this condition will never be matched as log as the more generic "/foo*" expression is at the top.
    }
    "/foo?bar" { 
         this will match any string that starts with "/foo", followed by any character, and followed by and ending with "bar". Except that this condition will never be matched as log as the more generic "/foo*" expression is at the top.
    } 
}

Generally speaking, you should always try to put the least specific matches at the bottom of the conditional. With "/foo*" at the top, the bottom two expressions can never be matched.