my %prefs;
...
eval {
  my $sth=$dbh->prepare("SELECT prefname, prefvalue FROM prefs WHERE user_login=?";
  $sth->execute($login);
  $sth->bind_columns( \my( $n, $v ) );
  while($sth->fetch)
  {
    $prefs{$n}=$v;
  }
};

if($@)
{
  #as before
}
#later to use
print "My favorite color is $prefs{color1}\n";
# or even
foreach my $p ( keys %prefs )
{
  print "I like my $p to be $prefs{$p}\n":
}