XPath expression to extract the hour offset from strin

Hi Folks,

I have strings that express time offset from UTC. Here are representative
examples:

UTC+5
UTC+1(+2DT)
UTC-11
UTC+4:30
UTC+9:30(+10:30DT)

In areas where daylight savings time is observed, the daylight savings time is
the part in parentheses.

Some offsets have both an hour and minute. The minute portion is after the
colon.

I need to extract the hour offset. So for the above examples, I need to
extract:

+5
+1
-11
+4
+9

This XPath expression seems to do the job:

let $time := "UTC+9:30(+10:30DT)" return
    if (contains($time,'(')) then
        let $part := substring-after(substring-before($time,'('),'UTC') return
            if (contains($part,':')) then
                substring-before($part,':')
            else
                $part
    else
        let $part := substring-after($time,'UTC') return
            if (contains($part,':')) then
                substring-before($part,':')
            else
                $part

Is there a better (simpler, shorter) XPath expression for doing this?

/Roger