Perl Tutorials - Herong's Tutorial Examples - Version 5.32, by Dr. Herong Yang
$$$name - Nested Symbolic References
This section provides a tutorial example on how to use nested symbolic references like $$$name, or $s->()->()->().
As mentioned in the previous section, symbolic references can be nested. Here is a tutorial program to prove that:
#- SoftRef4.pl #- Copyright (c) 1999 by Dr. Herong Yang, http://www.herongyang.com/ # $a = 'b'; $b = 'c'; $c = 'd'; $d = 'f'; $f = 'Hi there!'; print "$$$$$a\n"; print "${${${${$a}}}}\n"; $f = 'a'; print "$$$$$$$$$$$$$a\n"; print "$$$$$${$$$$$$$a}\n"; print 'x'->()->()->()->()->()->()->(), "\n"; sub x {return 'y';} sub y {return 'z';} sub z {return 'x';}
Here is the output of the tutorial program:
Hi there! Hi there! d d y
Do you understand why we are getting those values in the output?
Table of Contents
Data Types: Values and Variables
Expressions, Operations and Simple Statements
Name Spaces and Perl Module Files
►Symbolic (or Soft) References
$$name - Replacing Identifiers by Scalar Variables
${EXPR} - Replacing Identifiers by Expressions
EXPR->* - The Dereference Operator
►$$$name - Nested Symbolic References
Hard References - Addresses of Memory Objects
Objects (or References) and Classes (or Packages)
Typeglob and Importing Identifiers from Other Packages
String Built-in Functions and Performance
File Handles and Data Input/Output
Open Directories and Read File Names
File System Functions and Operations
Converting Perl Script to Executable Binary
Socket Communication Over the Internet
XML::Simple Module - XML Parser and Generator
SOAP::Lite - SOAP Server-Client Communication Module
Perl Programs as IIS Server CGI Scripts
CGI (Common Gateway Interface)
XML-RPC - Remote Procedure Call with XML and HTTP
RPC::XML - Perl Implementation of XML-RPC
Integrating Perl with Apache Web Server
CGI.pm Module for Building Web Pages