Perl Tutorials - Herong's Tutorial Examples
∟Symbolic (or Soft) References
∟$$$name - Nested Symbolic References
This section provides a tutorial example on how to use nested symbolic references like $$$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 "$$$$$a\n"; print "${${${${$a}}}}\n"; $f = 'a'; print "$$$$$$$$$$$$$a\n"; print "$$$$$${$$$$$$$a}\n"; print 'x'->()->()->()->()->()->()->(), "\n"; sub x {return 'y';} sub y {return 'z';} sub z {return 'x';}
Here is the output of the tutorial program:
Hi there! Hi there! d d y
Do you understand why we are getting those values in the output?
Table of Contents
About This Book
Perl on Linux Systems
ActivePerl on Windows Systems
Data Types: Values and Variables
Expressions, Operations and Simple Statements
User Defined Subroutines
Perl Built-in Debugger
Name Spaces and Perl Module Files
►Symbolic (or Soft) References
Using Symbolic References
$$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 Files in Binary Mode
Open Directories and Read File Names
File System Functions and Operations
Converting Perl Script to Executable Binary
Using DBM Database Files
Using MySQL Database Server
Socket Communication Over the Internet
XML::Simple Module - XML Parser and Generator
XML Communication Model
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
References
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