I use the POP3
I have seen the Net::POP3 module
It's always a good idea to include important details right from the start... :)
but can't extract the attachment file
Same here. What exactly is the problem? Is the attachment missing entirely? Are you unable to decode its transfer encoding (e.g. base64), etc.? Could you provide some complete (but short) raw example message, and possibly also some actual code, so we have an idea of what you've tried so far, and where you're stuck?