If you only want one row then do use
my @result = $dbh->selectrow_array("SELECT MAX(foo) FROM blah");

If you just want one column then
my @rows = @{ $dbh->selectcol_arrayref("SELECT id FROM blah") };

Otherwise do a full $dbh->selectall_arrayref as salvadors suggests or use the full prepare, execute, fetchrow syntaxes like you were doing originally.

For information on these syntaxes and more read up on the DBI docs.