Can someone point me to an example of using Mail::Field

You can try to use Super Search here at the Monastery. When I enter "mail::field" into the "Match text containing" field, there are admittedly few nodes. Perhaps some of them will help you. Here are a few that popped up:

• Clean unknown users/email from pop3 account
• Parse attachment file names from e-mail
• Re: Re: Finding e-mail headers

Maybe you can try other search strings as well.

You could also try looking at the source code of Mail::Field to see what the module is doing.

For others to see your related node: Brief Hash Tutorial