my %hash = %{$sth->fetchrow_hashref()};
[download]

while (my $row = $sth->fetchrow_hashref()) {
   my $mail = $row->{mail};
   print "$mail\n";
}
[download]

jeffa

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)

The same way you work with any other hash ref:

%hash = %$hashref;
# or to get at a specific value:
$value = $hashref->{key};
# or you can use fetchrow_arrayref:
my @names = @{$sth->{NAME_lc}};
my %hash;
while (my $values = $sth->fetchrow_arrayref) {
 @hash{@names} = @$values;
}
[download]

Two excellent specific answers to your question from jeffa and runrig are above. For more background, take a look at perlref and tye's very handy References quick reference.