+If the input line starts with ':<cmd>:', this prefix is removed and the
+line is processed by the runtest script before sending. The following
+commands are recognised:
+
+- "eval": process the reset of the line with Perl's string eval()
+ function. This can be used to send arbitrary data by encoding it as
+ escape sequences (e.g. "\x41\101"). If you need a line ending, you have
+ to append it accordingly (e.g. "\r\n").
+
+- "noeol": do not terminate the data sent to the application with an end
+ of line character.
+
+- "sleep": interpret the rest of the line as an integer and sleep for
+ that number of seconds before proceeding. No data will be output to
+ the application.
+
+
+ background
+
+This command takes one script line and runs it in the background,
+in parallel with following commands. For external daemons, eg. redis-server.
+