RunScript is working but not getEval

HI,
I am trying to call one javascript function getBoundaries to get some array value from the browser.
The function is working fine and returning the value in alert when I use runScript as;
selenium.runScript("alert(getBoundaries());");
But i want to read those values in selenium test since runScript doesn't return any values I am trying with getEval as:
selenium.getEval("javascript:{getBoundaries();}").
But it is throwing element not found error.
i also tried
selenium.getEval("javascript:{var arr=getLatLongBoundaries();alert(arr);}");


But no results....!

Please help me on this......!