Seeking new forms of expression in computer music, a small number of laptop composers are braving the challenges of coding music on the fly. Not content to submit meekly to the rigid interfaces of performance software like Ableton Live or Reason, they work with programming languages, building their own custom software, tweaking or writing the programs themselves as they perform. Often this activity takes place within some established language for computer music like SuperCollider, but there is no reason to stop errant minds pursuing their innovations in general scripting languages like Perl. This paper presents an introduction to the field of live coding, of real-time scripting during laptop music performance, and the improvisatory power and risks involved. The authors look at two test cases, the command-line music of slub utilising, amongst a grab-bag of technologies, Perl and REALbasic, and Julian Rohrhuber's Just In Time library for SuperCollider. They try to give a flavour of an exciting but hazardous world at the forefront of live laptop performance.