What are the ways to accomplish exact title searches with z39.50?

I'm looping through a list of MARC records trying to determine whether  
or not we own multiple copies of an item. After reading MARC field  
245, subfield a I am creating the following z39.50 query:

   @attr 1=4 "foo bar"

Unfortunately my local implementation seems to interpret this in a  
rather regular expression sort of way -- "* foo bar *". Does anybody  
out there know how to create a more exact query? I only want to find  
titles exactly equalling "foo bar".

-- 
Eric Lease Morgan
University of Notre Dame