Eric is correct, the FAQ is wrong.
The simplest patch is probably:
--- perlfaq7.pod 31 Jan 2003 17:38:14 -0000 1.14
+++ perlfaq7.pod 20 Jul 2003 06:09:30 -0000
@@ -809,5 +809,5 @@
use your own hash or a real reference instead.
- $fred = 23;
+ $USER_VARS{"fred"} = 23;
$varname = "fred";
$USER_VARS{$varname}++; # not $$varname++
=== Forwarded Message:
Date: Fri, 11 Jul 2003 09:40:56 -0500
From: Eric Pement <[EMAIL PROTECTED]>
Subject: Error in Sect. 7 on using a variable as a variable name
To: [EMAIL PROTECTED]
To whom it may concern:
In trying to learn about references, I believe I've found an error in
the Perl FAQ, section 7 ("General Perl Language Issues"), under the
question, "How can I use a variable as a variable name?" The problem
exists in the documentation for Perl 5.6 and Perl 5.8. I tried
emailing this message to "[EMAIL PROTECTED]" and got
no response. Now that I've got a newer email address, perhaps I can
get a reply.
The FAQ currently reads in part:
By using symbolic references, you are just using the package's
symbol-table hash (like %main::) instead of a user-defined hash.
The solution is to use your own hash or a real reference instead.
$fred = 23;
$varname = "fred";
$USER_VARS{$varname}++; # not $$varname++
This solution does not work and does not provide "24" as the FAQ
authors seem to have intended. This can be demonstrated like so:
#!/usr/bin/perl
use strict;
my ($fred, $varname, %USER_VARS);
$fred = 23;
$varname = "fred";
$USER_VARS{$varname}++;
print "Value is: $USER_VARS{$varname}\n";
The output is "Value is: 1". So how should this be corrected? Here's
a replacement I suggest for the FAQ. It returns "24", as expected:
$USER_VARS{fred} = 23;
$varname = "fred";
$USER_VARS{$varname}++; # not $$varname++
Finally, the FAQ says another solution is to use a real reference
instead. Perhaps you could tell new perl users how this is done:
$fred = 23;
$varname = \$fred;
$$varname++;
Thanks in advance for your time.
--
Eric Pement - [EMAIL PROTECTED]
Education Technical Services, MBI
=== End of Forwarded Message
