Depending on how close you want to stay to cURL, look either at LWP::UserAgent or at cURL.

Using LWP::UserAgent together with HTTP::Request::Common should be fairly easy to send the messages:

my $ua= LWP::UserAgent->new();
my $res= $ua->post( $url, { username => 'testusergoeshere@gmail.com', 
+password => 'somecoolpassword' });
$res->dump;
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