Further to haj's reply ...

According to the code examples posted so far in this thread, SES::call_ses does not appear to be a method of the SES class, so assigning to a $self variable, which is, by convention, usually used to denote an object reference to or the class name of a class method, makes no sense.

In the invocation
    my ($response_code, $response_content) = SES::call_ses \%params, \%opts;
\%params is not a bless-ed reference (i.e., an object reference) of any kind, so don't treat it as such in a call to $self->AWS_endpoint in the

sub call_ses {

    my $self = shift;

    ...

    my $endpoint_name = $self->AWS_endpoint;

}
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function.

SES::call_ses seems to be an ordinary subroutine defined in the SES package. This subroutine does not seem to be exported, so it must be invoked via the fully-qualified SES::call_ses syntax. According to the error message, this subroutine was called with two arguments, so shifting three arguments off of the @_ argument array will leave someone holding an undefined bag. Don't do that.