empty row sometimes?

[misc]

hello all,
  I worked out what I need to do, but I'm not 
sure why the first thing I tried did not work.
observe the following code snippet:

$qry = "SELECT * FROM table WHERE field=5";
$sth = $dbconn->prepare($qry);
$sth->execute or die($sth->errstr); 
$row1 = $sth->fetchrow_hashref;
print " got here ** ";
if ($row1 not "") {
 print "row not empty";
} else {
  print "row is empty";
}    

when my SQL query returns no rows
this prints out:
 got here ** row is empty

now the following code:

$qry = "SELECT * FROM table WHERE field=5";
$sth = $dbconn->prepare($qry);
$sth->execute or die($sth->errstr);
$row1 = $sth->fetchrow_hashref;
$temp = $$row1{'field'};
print " got here ** ";
if ($row1 ne "") {
 print "row not empty";
} else {
  print "row is empty";
}    

with the same SQL statement and database
prints out:
 got here ** row not empty 

why?  why is the reference not undef still
in the second case?  By dereferencing an
undef reference it becomes defined?  Isn't
that akin to raising the dead?  I am running activestate Perl 5.004 under win98se.  I 
am 
using DBD::ADO and an access2000 database.

thanks for any help,
andrew