my %hash;
$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 qw(keys %hash);

foreach $key (keys %hash) {
    eval("$key=\"$hash{$key}\"");
    print "  $key=$hash{$key}\n";
}

system("printenv");