Question

I am currently developping a multi-environment perl script. As you all know, environment configuration juggling could be quite a pain if badly done. As my perl script must allow some command line parameters in a configuration value overload purpose, i came with the following solution :

package Cfg;
use strict;
use warnings;
my $gEnvironment = "DEBUG";#"PRODUCTION";
my %gConfig = (
  DEBUG=>{MESSAGE=>"This is a dbg env.",URL=>"www.my-dbg-url.org"},
  PRODUCTION=>{MESSAGE=>"This is a prod env.",URL=>"www.shinyprodurl.org"}
);
my $gMessage = defined $gConfig{$gEnvironment} ?
  $gConfig{$gEnvironment}{MESSAGE} : die "Crappy environment";
sub Message { $gMessage = shift(@_) if (@_); $gMessage }
sub Url {
  defined $gConfig{$gEnvironment} ?
    $gConfig{$gEnvironment}{URL} : die "Crappy environment"
}
1;

So, the following script :

use strict;
use warnings;
use Cfg;
print Cfg::Message,"\n";
Cfg::Message("I'm a surcharged message.");
print Cfg::Message;

Would produce the next output:

This is a dbg env.
I'm a surcharged message.

The point is I want to define $gEnvironment’s value during the loading of the Cfg module.
This would allow me to use the same configuration module in all my environments.

Is this possible ?

Answer 1

I believe a custom import method is what you’re after:

package Cfg;

our $gMessage;

sub import {
    my ($package, $msg) = @_;
    $gMessage = $msg;
}

and somewhere else:

use Cfg "some message";

import is what perl will call when you use some module. Please see perldoc -f use for the details.