Nothing in the HTTP::Tiny docs but it is in the code: 
# line 239
sub post_form {
    my ($self, $url, $data, $args) = @_;
    # ...
    delete $args->{headers};

[download]

The request() method doesn't seem to do this deletion.

In reply to Re^3: HTTP::Tiny losing headers for Stripe by tangent
in thread HTTP::Tiny losing headers for Stripe by Bod

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