Unrelated to your main problem...

%ENV = { %ENV, %BB_ENV };

If you use strict and warnings, it will alert you that there is something wrong with this way of merging hashes:

use warnings;
use strict;
use Data::Dumper;

my %BB_ENV = (zzz => 555);
%ENV = { %ENV, %BB_ENV };
print Dumper(\%ENV);

__END__

Reference found where even-sized list expected at 
$VAR1 = {
          'HASH(0x6f45f0)' => undef
        };
[download]

diagnostics shows that you should use parens () instead of curlies {}.