How to replace every backslash in an input form token with a double backslash

Hello, please I would like to know how I can replace a single "\" backslash with a double "\\" backslash in a form input (simple xml) before submitting it. I have tried with this code, but it does not work with splunk 6.5.x Progetto (raddoppiare i "\")**replace('progetto',"\\\","\\\\\\") Thanks in advance.