Content-type: multipart/form-data, boundary=AaB03x; extra=whocares

--AaB03x
content-disposition: form-data; name="field1"

Joe Blow
--AaB03x
content-disposition: form-data; name="pics"
Content-type: multipart/mixed, boundary="BbC04y"

--BbC04y
Content-disposition: attachment; filename="file1.txt"
Content-Type: text/plain

... contents of file1.txt ...
--BbC04y
Content-disposition: attachment; filename="file2.gif"
Content-type: image/gif
Content-Transfer-Encoding: binary

  ...contents of file2.gif...
--BbC04y--
--AaB03x--

