How do I define an anonymous scalar ref in Perl?

Question

How do I properly define an anonymous scalar ref in Perl?

my $scalar_ref = ?;

my $array_ref = [];

my $hash_ref = {};

Answer 1

If you want a reference to some mutable storage, there's no particularly neat direct syntax for it. About the best you can manage is

my $var;
my $sref = \$var;

Or neater

my $sref = \my $var;

Or if you don't want the variable itself to be in scope any more, you can use a do block:

my $sref = do { \my $tmp };

At this point you can pass $sref around by value, and any mutations to the scalar it references will be seen by others.

This technique of course works just as well for array or hash references, just that there's neater syntax for doing that with [] and {}:

my $aref = do { \my @tmp };  ## same as  my $aref = [];

my $href = do { \my %tmp };  ## same as  my $href = {};