The first piece of code seems "valid" to me. Could you specify what exactly fails?

As for the second snippet, you have a typo in there (print $row->{'count(*)} you forget an apostrophe (') ). I would write it something like this (to make it more readable):

$st = $db->prepare("SELECT count(*) AS total FROM members");
$st->execute();
my $row = $st->fetchrow_hashref();

print $row->{total}."\n";
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Update: You can use your approach, but don't forget the apostrophe (single quote):

print $row->{'count(*)'}."\n";
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