ちなみにHTMLはこんなの。
<html>
<head>
<title>upload</title>
</head>
<body>
<form action="/cgi-bin/print.rb" method="post" enctype="multipart/form-data">
<input type="file" name="filename" size="32" maxlength="256"></input>
<input type="submit" value="submit">
</form>
</body></html>