Most characters that can be typed at your keyboard are TECO
  commands.  Use them with care.

  All TECO commands are terminated with the <ESC> character,
  which will echo as a "$" at your terminal.  To execute a
  command (or string of commands), type a second <ESC> after
  the last command in the string.  No TECO command will be
  executed until two consecutive <ESC>s are typed.  <ESC> may
  be labeled <ALT-MODE> or <PREFIX> on your terminal.