Adding shell command example.

README.md

@@ -1,3 +1,19 @@
 # MailExample
 
-A demostration that sending mails with multipart/alternative choice between text and html is not that difficult.
+A demostration that sending mails with multipart/alternative choice between text and html is not that difficult.
+
+Example usage:
+
+```shell
+cpan .
+
+cat <<'EOF' > mail_text_file.txt
+hola mundo
+EOF
+
+cat <<'EOF' > mail_html_file.txt
+<h1>hola mundo<h1>
+EOF
+
+mail_example --user <sasl_user> --port 465 --host <smtp_host> --password <sasl_password> --subject hola --to <destination address> --text_body_file mail_text_file.txt --html_body_file mail_html_file.txt
+```