See: Perseus under PhiloLogic.
Perseus Project Texts Loaded under PhiloLogic, Greek and Latin Morphology (current Release #2, April 2010)
From the Info, FAQ and help page, by Helma Dik (excerpts):
The texts made available are practically all used by permission from the Perseus Project at Tufts University. However, the mechanism for browsing and searching the Perseus Project texts is a different one. It is PhiloLogic, an open-source system that was especially developed for large textual databases by the ARTFL project at the University of Chicago.
The Perseus under PhiloLogic collection is intended to use the rich encoding for searching the texts, and for other tasks that are less about reading and more about research: corpus linguistics, above all.
Currently it is possible to search not only for words or strings, but also for occurrences of a lemma or part-of-speech code, thanks to prefixes 'lemma:' or 'pos:'. For example, 'lemma:nostos' or 'lemma:sum'.
The prefix 'form:' ignores the more complex instructions for part-of-speech codes that follow. You simply write out what you think will sufficiently describe the form you are looking for, in any order, but use hyphens between terms. For instance, 'form:optative-act-singular' for an active optative in the singular, where 'form:sg-opt-act' would do the same thing.