Perl $$var — two dollar signs as a sigil?

Question

This seems like something I should be able to easily Google, Bing, or DDG, but I\'m coming up completely empty on everything.

Basically, I\'m tasked with (in part) r

Answer 1

This is an alternative form of dereferencing. Could (and honestly probably should) be written as:

$LOC->{'DESCRIPTION'};

You'll sometimes see the same with other all basic data types:

my $str = 'a string';
my %hash = (a => 1, b => 2);
my @array = (1..4);

my $strref = \$str;
my $hashref = \%hash;
my $arrayref = \@array;

print "String value is $$strref\n";
print "Hash values are either $$hashref{a} or $hashref->{b}\n";
print "Array values are accessed by either $$arrayref[0] or $arrayref->[2]\n";

Answer 2

Dereferencing is treating a scalar as the 'address' at which you can locate another variable (scalar, array, or hash) and its value.

In this case, $LOC{DESCRIPTION} is being interpreted as the address of another scalar, which is read into $comment.

In Perl,

my $str = 'some val';
my $ref = \$str;
my $val = ${$ref};
my $same_val = $$ref;