When submitting forms with (known binary) files with the "curl" http-client, php fails to recognize the content-transfer-encoding header, causing the file to be crippled. (The header (except the first character) is placed in the file along with the data).

Let me quote a phrase from section 3.3 of RFC 1867:

   The value supplied for a part may need to be
   encoded and the "content-transfer-encoding" header supplied if the
   value does not conform to the default encoding.