How do I check if a Perl scalar variable has been initialized?

Question

Is the following the best way to check if a scalar variable is initialized in Perl, using defined?

my $var;

if (cond) {
    $var = \"string1\";         


        

Answer 1

It depends on what you plan on doing with the variable whether or not it is defined; as of Perl 5.10, you can do this (from perl51000delta):

A new operator // (defined-or) has been implemented. The following expression:

 $a // $b

is merely equivalent to

defined $a ? $a : $b

and the statement

$c //= $d;

can now be used instead of

$c = $d unless defined $c;