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

In the case of the code you posted, I would also do as ikegami said, and use the shorter form.

There are occasions when that isn't suitable, however, for example if a variable could have a legitimate value that would be treated as false if simply used in a true/false test. For example:

my $value = 0;
print "defined\n" if defined $value;  # prints 'defined'
print "true\n" if $value;  # does not print anything