Since use happens at compile-time, %hash is empty. That's not really a problem here, since keys %hash is treated as a literal string by qw//. Since you're not importing what you think you're importing, your eval fails. Since you're not checking $@, you don't know this.

I'd really rather write:

but if you really want to get your way to work, here's a start. I'm not sure if Env returns lvalue subs, though:

#!/usr/bin/perl -w

use strict;

my %hash;
BEGIN
{
    $hash{APP_DIR} = "/usr/vendor/app/version/";
    $hash{TMP_DIR} = "/usr/tmp/";
    $hash{PROJ_DIR} = "/usr/people/userid/app/";
    $hash{APP_LOCATION} = "/usr/vendor/app/version/bin/";
}

use Env (keys %hash);

foreach my $key (keys %hash) {
    eval("$key=\"$hash{$key}\"");
    print "Eval error '$@'\n" if $@;
    print "  $key=$hash{$key}\n";
}

system("printenv");
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BEGIN {
  $ENV{APP_DIR} = "/usr/vendor/app/version";
  # etc.
}

system("printenv");  # should have the new keys in it
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I suspect you don't want 'keys' and '%hash' to be the two arguments in use Env ...;, but that's what qw() is giving you. Omit the qw and you will get a list of the keys.

I don't see why you use Env.pm, though. If you do as you are to %hash with the special %ENV hash, all will be well.

After Compline,
Zaxo

What you need to do is explained (very briefly) in perlvar, which explains that fork() will propagate changes to %ENV. So, instead of loading up %hash, change %ENV and then fork. Try forking to "printenv" as a quick test.

Hmm, the following works for me on two Unix-like boxes (Mac OS X and GNU/Linux):

use strict;
%ENV = ( foo => 'bar ');
system( 'printenv' );
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Looking in the code for system, it forks internally, which is what I'd expect. I wouldn't expect this to be very portable outside of Unix, though.

dws,
I thought this too and almost replied, but I got distracted. It would be good to point out that while you can change "set" the environment that you fork (child process), you can't export it back to the parent. I was guessing that the OP was trying to do the equivalent of:

$ perl -e 'cd /tmp'
$ pwd
 /home/user
$ echo "WTF?"
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Cheers - L~R

Update: I can neither confirm nor deny it (without research anyway), but I heard this actually works on VMS. And while you can set the parent to read information from the child and set the parameters itself in the OS's I was originally referring to, the child is not actually doing it.

use Env qw[ APP_DIR TMP_DIR PROJ_DIR APP_LOCATION ];

$PROJ_DIR = '/usr/people/userid/app/';
$APP_DIR = '/usr/vendor/app/version/';
$APP_LOCATION = '/usr/vendor/app/version/bin/';
$TMP_DIR = '/usr/tmp/';

system 'printenv';
__END__
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use Env qw[ $PATH @PATH];
print "$PATH\n";
print "$_\n" for @PATH;
__END__
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MJD says "you can't just make shit up and expect the computer to know what you mean, retardo!"

I run a Win32 PPM repository for perl 5.6.x and 5.8.x -- I take requests (README).

** The third rule of perl club is a statement of fact: pod is sexy.

foreach my $x ( sort keys %ENV ) {
   print "$x  --  $ENV{$x}\n";
}
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First, though, chromatic suggested %ENV{ keys %hash } = values %hash; which I tried right away, only to get a syntax error. Not certain what was failing, I went to japhy's suggestion and came up with:

foreach $key (keys %hash) {
    $ENV{$key} = $hash{$key};
}
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As for all of the other suggestions, they mostly had to do with my clumsy creation of the hash. My example code was significantly simpler than what I'm really doing, and I was trying provide you with a simple hash for testing. It was the use Env qw(keys %hash); that was really the hack, and it turns out that I misread an example somewhere on this site that was meant for multi-valued vars (thanks for the heads-up, PodMaster).

My real code takes in the hash as a parm using Getopt and then passes it to a sub intended to set the environment vars to their corresponding values in the hash:

#!/usr/bin/perl

use strict;
use warnings;
use Getopt::Long;

my %engEnvVars;

GetOptions (
    "engEnvVar=s" => \%engEnvVars
)

sub setEnvVars {
    my %engEnvVars = @_;

    my $key;

    foreach $key (keys %hash) {
        $ENV{$key} = $hash{$key};
    }

    system("printenv") if $DEBUG;
}

setEnvVars(%engEnvVars);
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./testScript.pl -engEnvVar APP_DIR=/usr/vendor/app/version/ -engEnvVar
+ TMP_DIR=/usr/tmp/
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Yes, dws was correct in that I am setting these environment variables so that I can call another application.

I tested chromatic's second example:

use strict;
%ENV = ( foo => 'bar ');
system ( 'printenv' );
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What a long, arduous path for me. Finding this site and sharing my questions shows me how little I really know about Perl. I appreciate all of your input. Thank you.

-- ccarden