Interpolating Variables as Package Names

dReKurCe has asked for the wisdom of the Perl Monks concerning the following question:

Greetings Monks;

I am trying to intropolate a variable from a different package into a here document as follows:


#! /usr/bin/perl;

 unshift @INC, "/path/to/package";

 print "Introplate variables from which package?";

 $package=<STDIN>;

 use $package; 

 print << EOF;

 This variable:

 #heres the intropolation I want to effect:

 $package::variable

 originates in package $package.

 EOF
[download]

So the problem I am trying to solve is the intropolation of the package name into the $packagename::variable format. What is the most correct approach to solving this?

Thank you

Comment on Interpolating Variables as Package Names Download Code

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Re: Interpolating Variables as Package Names by Roy Johnson (Monsignor) on Mar 09, 2005 at 20:22 UTC
I'm dumping my previous answer in favor of pointing you here. At least until I figure out a concise answer. Update: Ok, I worked it out: `use strict; use warnings; package foo; our $var = 'got it'; package main; my $pkg = 'foo'; my $v = 'var'; print ${$main::{$pkg.'::'}{$v}};` [download] Note that you get no hassles about symbolic references. "main::" is the name of the hash that includes the symbol tables for all the other packages. You index it by the package name (with double-colon appended), and then the variable name. That gives you a glob reference, which you can dereference using the appropriate sigil. Caution: Contents may have been coded under pressure.	[reply] [d/l]
Re^2: Intropating Variables as Package Names by dReKurCe (Scribe) on Mar 09, 2005 at 22:31 UTC
An amazing solution!Thanks for the help!	[reply]
Re: Intropating Variables as Package Names by crashtest (Curate) on Mar 09, 2005 at 20:22 UTC
`use` is done at compile time in a `BEGIN` block. If you want to dynamically load a package at run time, you want require instead. The below code worked for me: `#!/usr/bin/perl; unshift @INC, "/path/to/package"; print "Interpolate variables from which package? "; $package = <STDIN>; chomp($package); eval "require $package"; print <<EOF; This variable: $package::variable (actually this doesn't work) originates in package $package. EOF` [download] Update:: gaal is absolutely right, the code will not show the correct package variable. I was more focused on showing how to load modules at runtime. Roy Johnson seems to have the interpolation part worked out.	[reply] [d/l] [select]
Re^2: Intropating Variables as Package Names by gaal (Parson) on Mar 09, 2005 at 20:27 UTC
`$package::variable` looks for a dynamic variable called `$variable` in the package `package::`. As Roy Johnson said, you need to look in the symbol table of `$package`.	[reply] [d/l] [select]


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