Hello Nicpetbio23!,

Just to add something here to analytical explanation by fellow monk stevieb. You can use also the functions undef and defined.

Usually you do not check for a scalar as my example bellow but if a scalar exists specifically in a hash (usually). But just for demonstration purposes see bellow:

#!/usr/bin/env perl
use strict;
use warnings;

my $scalar = undef;

if (defined $scalar) {
    print "\$scalar is defined\n";
}
else {
    print "\$scalar is undefined\n";
}

__END__
$ perl test.pl
$scalar is undefined
[download]

Hope this helps, BR.