<wob_jonas> perl -eopen$i,"<",($f="wisdom/aristotle");$_=<$i>; s/two thousand/2000/ or die; if (1) { open$o,">",$f; print$o $_ or die; } print substr$_,0;

cat introduction is the process of piping one or more extra `cat` commands into your pipeline; occasionally this is even actually useful.