+=head1 PROTOCOL
+
+Each byte of the data string is converted into its bits sequence, with bits of highest weight coming first. All those bits sequences are put into the same order as the characters occur in the string.
+
+The header is composed by the C<utf8> bit (if the data has to be decoded to UTF-8), the C<sign> bit (if sender gives its PID in the header), and then 24 bits representing the sender's PID (with highest weight coming first) if the C<sign> bit is set.
+
+The emitter computes then the longuest sequence of successives 0 (say, m) and 1 (n) in the concatenation of the header and the data. A signature is then chosen :
+
+=over 4
+
+=item - If m > n, we take n+1 times 1 follewed by one 0 ;
+
+=item - Otherwise, we take m+1 times 0 follewed by one 1.
+
+=back
+
+The signal is then formed by concatenating the signature, the header, the data bits and the reversed signature (i.e. the bits of the signature in the reverse order).
+
+ a ... a b | u s [ p23 ... p0 ] | ... data ... | b a ... a
+ signature | header | data | reversed signature
+
+The receiver knows that the signature has been sent when it has catched at least one 0 and one 1. The signal is completely transferred when it has received for the first time the whole reversed signature.
+
+=head1 CAVEATS
+
+This type of IPC is highly unreliable. Send little data at slow speed if you want it to reach its goal.
+
+C<SIGUSR{1,2}> seem to interrupt sleep, so it's not a good idea to transfer data to a sleeping process.
+