Thanks for your mail.
Take this input:
<div id="ps-content">foobar</div>
and apply this XPATH 2+: //div[matches(@id,"^s-content$")]
I just tried the following query..
<div id="ps-content">foobar</div>[matches(@id,"^s-content$")]
..and I got no result. Which BaseX version are you working with? Can you give us some more details?
Christian