foreach $key (keys %hash) {
    $ENV{$key} = $hash{$key};
}
##</code><code>##

#!/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);

##</code><code>##

./testScript.pl -engEnvVar APP_DIR=/usr/vendor/app/version/ -engEnvVar TMP_DIR=/usr/tmp/

##</code><code>##

use strict;
%ENV = ( foo => 'bar ');
system ( 'printenv' );