This section describes how to use hard references - hard references are used in the same way as soft references by replacing identifier with a hard reference expression in curly brackets {}, or using the dereference operator ->.
Similar to soft (symbolic) references, there several syntax formats to use hard references:
1. Directly placing a scalar variable that contains the hard reference in the
place where the identifier should be.
For example, $ref = \$foo; $$ref = 10; print "$foo";
2. Placing an expression that returns a hard reference in curly brackets {}
to replace the identifier.
For example, $ref = \$foo; ${$ref} = 20; print "$foo";
3. If a hard reference is used to access a single element of an array, to access
a single element of hash, or to call a function, you can remove the name space
prefix character $, or &, and replace the identifier with an expression that
returns the hard reference, then followed by the dereference operator: ->.
For example, $ref = \@foo; $ref->[0] = 30; print "$foo[0]";
4. Of course, hard references can be nested. They can also be mixed with
soft (symbolic) references.
For example, $a = \$b; $b = \$c; $c = 40; print "$$$a";
Another example is: $a = \$b; $b = 'c'; $c = 50; print "$$$a";
