protects all regexp special characters

gistfile1.xquery

(: 
 : protects all regexp special characters
 : @author Marc van Grootel
 : @see http://www.mail-archive.com/basex-talk@mailman.uni-konstanz.de/msg04573.html
 :)
declare function route:re-escape($string as xs:string)
    as xs:string {
    let $regexp-chars :=  ('.','*','+','|','?','(',')','[',']','{','}','^')
    return
        (: Note that '\' and '$' in the fold caused invalid pattern errors therefore put them in separate replace :)
        fold-left(
            $regexp-chars, 
            replace(replace($string, '\\', '\\\\'), '\$', '\\\$'), 
            function($a, $b) {
                replace($a, '\'||$b, '\\'||$b )
            }
        )
};