perhaps the following code might give you a key what to do:

#!perl -w
use strict;

my (%variable) = ( 'EngineConfigDir' => 'c:\Daily\DreBa_Connect_Engine
+\Config');
&SetSystemVariable(\%variable);

# ------------------------------------------------------------
sub SetSystemVariable {
    my ($variable) = @_;

    # well, this should be in the head of your script
    # I just put it here to complete the function
    use Win32::TieRegistry( ArrayValues=>0 );

    my $pound= $Registry->Delimiter("/");
    my $systemVariable = 
    $Registry->{"LMachine/SYSTEM/CurrentControlSet/Control/Session Man
+ager/Environment"} or 
        die ("Can't find root\n");;


    # set systemvariable
    foreach (keys %$variable){
        $systemVariable->{"/$_"} = $variable->{$_};
    }
    my $systemVariable2 = 
    $Registry->{"LMachine/SYSTEM/CurrentControlSet/Control/Session Man
+ager/Environment"} or 
        die ("Can't find\n");;
    foreach my $key (keys %$systemVariable2){
        print ("$key => $systemVariable->{$key}\n") if (grep { $key eq
+ "/$_" } keys %$variable);
    }

} # SetSystemVariable
# ------------------------------------------------------------
[download]

I used it about two years ago to set an environment variable called EngineConfigDir. But I'm afraid a little bit more error handling is necessary.

Best regards,
perl -e "s>>*F>e=>y)\*martinF)stronat)=>print,print v8.8.8.32.11.32"