twitter hashtag autolinking in query

hashtag.xq

xquery version "3.0";

let $trim := function($arg){
replace(replace($arg,'\s+$',''),'^\s+','')
}

let  $hashTag := function( $input ){
  let $flags := ''
  let $pattern := "(^|\s)((#)([A-Za-z]+[A-Za-z0-9_]{1,15}))(\s|$)"
  let $replacement := '<span>$1<a href="/tag/$3">$4</a>$5</span>'
  return  replace($input, $pattern , $replacement, $flags )
}

let $flags := 's'
let $input := $trim($model('page-content')/*/text())
let $pattern := "(\n)"
let $seqLines := tokenize($input, $pattern)

let $lines := map(function($line) {
let $replaced := '<div>' || $hashTag($line) || '<br/></div>'
let $l := util:parse($replaced )
   return
    ( $l/*/node())
    }, $seqLines)

xquery regex for twitter style hashtags