I would output the arguments to the second post_form call just before it occurs.

Bingo! - Thank you very much hippo

That explains what is going wrong...the authorization parameter is missing...

It doesn't explain why it is going wrong.

Using this code:

print "Content-type: text/plain\n\n";

my $headers = {
    'headers'       => {
        'Authorization' => 'Bearer ' . $Site::Variables::stripe_secret
+,
    },
    'agent'         => 'Wayfinder/v3.0',
};

my $sub_id = 'sub_xxxxxx';

print Dumper $headers;
print "\n\n--------------\n\n";

# This line is the culprit...
my $res = $http->post_form("https://api.stripe.com/v1/subscriptions/$s
+ub_id", {}, $headers);

print Dumper $headers;
print "\n\n--------------\n\n";
[download]

I get this output:

$VAR1 = {
          'headers' => {
                         'Authorization' => 'Bearer sk_test_abc123'
                       },
          'agent' => 'Wayfinder/v3.0'
        };


--------------

$VAR1 = {
          'agent' => 'Wayfinder/v3.0'
        };


--------------
[download]

Somehow the $header is being changed during the first call. I see nothing in the documentation for HTTP::Tiny to explain this.

In the short-term I can work around the problem by recreating $header between calls to Stripe. But it's not a very good solution.

I would also try to fix this first

Ordinarily, I would have fixed the API call first. However, the call requires data from the first call in order to work. Hence the need for two calls to the API.