"Full" versions versus "Preliminary" version of result/paper. Are they considered different? This is a common pattern in publications, not exclusive to my field (TCS):


  An author submits a paper to a conference (as preliminary version). Then, after acceptance to a conference, virtually the same paper (modulo some modifications, etc mostly in length but rarely in any conceptual level) is submitted to a journal, possibly with a different title (but not always). The latter is called full version. In many cases, the two versions are indistinguishable and in most cases epsilon away (for a small epsilon).


At the end, the author has two publications (conference+journal) from practically the same technical result.


  Is this considered as one or two publications? (technically of course are two different publications, but how people perceive that?)


From what I have seen, this is generally considered as 2 publications. So, an author with 5 results that follows the above pattern will have 5 conferences + 5 journals = 10 publications. Another author with again 5 results that are submitted only directly to journals (for one reason or the other, for example lack of travel funding from the institution) will have only 5 publications and, subsequently, will be ranked lower than the first author/candidate. 


  My question is:  How do academic people perceive the same publication that has been published in a conference as a short version and, subsequently, in a journal as a long version where both versions contain virtually the same text/results. How can someone evaluate this when sometimes these two publications appear with a different title?
I don't think this question has a universal or near-universal answer.  Different people, or even sometimes the same person in different contexts, will count differently if they need to count at all.

More generally, I don't think anyone actually makes decisions based on raw counts of papers, though plenty of people try to justify their decisions to others based on raw counts.

Two versions of the same paper count as two if the person doing the counting wants to make you look better and count as one if the person doing the counting wants to make you look worse.