No doubt, it's just that the line appeared in wackattack's code, not the code he said he used as a reference for using the Bio modules. I do know who Lincoln Stein is, but I wondered if in following some other example a little too closely, the Bio modules had been installed in an unconventional place on wackattack's system. That sort of thing occasionally happens.
For the original poster, the special global array @INC contains the paths which perl uses to find scripts and libraries for "do filename;", use and require commands. This is just general information, and isn't nearly as useful as perldoc -l (per chromatic). :)