FLAGS (\Seen) UID 42 RFC822.TEXT {234565}
this is a bunch of string data, but 
it also contains some binary data...it's not actually
IMAP code, it's an internal app that works similarly, but
a lot more people are more familiar with IMAP...
..snip..
a lot more string
 RFC822.SIZE 234565  INTERNALDATE " 21 FEB 2016 12:23:23 +1000")

##</code><code>##

while( $sz > 32760 ) {
   $m =~ /(^.{32760})/g;
   print $FH $1;
   $sz -= 32760;
}
$m =~ /(^.{$sz})/g;
print $FH $1;