[devote]

типо этого чтоль:

var m;

var url = "http://www.google.com/search?sourceid=chrome&ie=UTF-8&q=javascript+ru";

if ( m = /(?:q=)(.*?(?=[^A-Za-z0-9_\+])|.*$)/g.exec( url ) ) {
    alert( m.join("\n\n") );
}

var url = "http://www.google.com/search?sourceid=chrome&ie=UTF-8&q=javascript+regex+Invalid+group#hl=ru&gs_nf=1&pq=javascript%20%D0%B8%20php%20regexp%20%D0%BE%D1%82%D0%BB%D0%B8%D1%87%D0%B8%D1%8F&cp=7&gs_id=c3&xhr=t&q=javascript+ru&pf=p&sclient=psy-ab&oq=%D0%BE%D1%84%D0%BC%D1%84%D1%8B%D1%81%D0%BA&gs_l=&pbx=1&bav=on.2,or.r_gc.r_pw.r_cp.r_qf.,cf.osb &fp=35bf63437e7f3d7e&biw=1920&bih=1099";

if ( m = /(?:q=)(.*?(?=[^A-Za-z0-9_\+])|.*$)/g.exec( url ) ) {
    alert( m.join("\n\n") );
}