Using Symbolic References

Perl Tutorials - Herong's Tutorial Examples - Version 5.32, by Dr. Herong Yang

Perl Tutorials - Herong's Tutorial Examples

∟Using Symbolic References

This section describes symbolic (or soft) references, replacing variable or function identifiers by string expressions. Curly brackets {} or the dereference operator -> is the best way of using symbolic references.

Symbolic references are scalar objects containing strings representing identifiers of variables and functions. Symbolic references are also called soft references. There are several ways to use symbolic references.

1. Directly placing a scalar variable that contains the referencing string in the place where the identifier should be. For example, $name = 'foo'; $$name = 10; print "$foo";

2. Placing an expression that returns the referencing string in curly brackets {} to replace the identifier. Curly brackets are also called lookups. String literals in lookups don't have to be quoted. For example, $name = 'foo'; ${$name.'l'} = 20; print "$fool";

3. If a symbolic 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 referencing string, then followed by the dereference operator: ->. For example, $name = 'foo'; $name->[0] = 30; print "$foo[0]";

4. Of course, symbolic references can be nested. For example, $a = 'b'; $b = 'c'; $c = 40; print "$$$a";

See next sections for more examples on symbolic references.

Table of Contents

About This Book

Perl on Linux Systems

ActivePerl on Windows Systems

Data Types: Values and Variables

Expressions, Operations and Simple Statements

User Defined Subroutines

Perl Built-in Debugger

Name Spaces and Perl Module Files

►Symbolic (or Soft) References