When to use defined

Question

I am a little confused as which way to test parameters. Here are two examples from source code posted below. First is this

if(!defined($DBHdl) || !defined($ac

Answer 1

$sth->fetchrow_hashref will either return undef or a reference to a hash. As such

if (defined($row))

and

if ($row)

are equivalent here. (undef is false, and reference is always true.) I opt for the simpler alternative.

Same idea for $dbh->prepare.