Let's remember: "api" blocks and wait for result, "bgapi" returns immediately giving you an uuid you will use to recognize the results.

#!/usr/bin/perl 
require ESL; 
 
my $con = ESL::ESLconnection->new("localhost", "8021", "ClueCon"); 
 
$con->api('chat', "sip|[email protected]|[email protected]|ciao a tutti1|text/plain"); 
$con->bgapi('chat', "sip|[email protected]|[email protected]|ciao a tutti2|text/plain");