There are Indo-European cognate pairs that are phonetically exact and regular in the sense that their phonematic make-up is completely explained by systematic application of the relevant sound rules to a reconstructed PIE form that does not involve any consideration of paradigmatic levelling, contamination, irregular assimilations etc.
An example of such a cognate pair would be work and έργο, which are connected somehow like this:
work < weorc < *werk < *werką < *wérǵom > *wérgon > ἔργον > έργο
(The point being, every stage in the above derivation uses sound shifts that might be considered 'exceptionless' in the analysis of this pair, and the derivation is exhausted by such regular sound shifts. I have not checked the OE > ME stage myself for ignorance of Germanic linguistics but I assume that even if this particular pair is not entirely regular then surely there are other cognate pairs across IE which would be.)
Having a list of sound changes for the relevant (proto-)languages to hand, we could theoretically automatize the process of their application to Modern English and Modern Greek, so that a computer can run the whole thing for us and, when we input 'wɜːk', to output 'ˈeɾɣo' (along with other phonetically exact and regular cognates which could have been possible), all this with no reference to a dictionary of Modern English, Modern Greek or a PIE lexicon but relying solely on the list of sound changes we program it with. The same could be done with other pairs of IE languages, obviously.
Has such a computer program ever been written?