You can loop through the records in u_pers_name and check to see if it contains the any of the names in sys_user via the indexOf method.

var gr = new GlideRecord('sys_user');

      gr.addQuery('first_name','Anna Marie');

      gr.query();

if(gr.next())

{

      var name = gr.first_name;

      var names = name.split(' '); // splitting this on a space.

      gs.print(names[0] +" and other split is " + names[1])//just checking the split

      var gl = new GlideRecord('u_validation');

                  gl.query();

        while(gl.next())

        {

                  if(names.indexOf(gl.u_pers_name) == -1)

                  { // the -1 indicates that the value passed in does not have a position within the array.

                            gs.print(names.toString());

                  }

        }

}

Slightly less efficient, but you'll probably get more accurate results, when the data is that variable.