Present Perfect: Endings

Bear in mind that this tense is called [present] perfect because we can see (now, in the present) the result of what has been perfected, done, carried out, achieved.

Philip sees a hare and lets the dog off the lead:
ὁ μὲν Φίλιππος λαγὼ ὁρᾶ, λύει οὖν τὸν κύνα.
Now Philip has let the dog go, see Argos running after the hare.
ὁ Φίλιππος ἤδη λέλυκε τὸν κύνα, ὅρα τὸν Ἀργὸν μετὰ τὸν λαγὼ τρέχοντα.

Active Voice κ inserted between stem and thematic vowel, α in all endings except 3rd person singular (he-she-it) which takes an ε and a movable ν if followed by a punctuation mark or by a word beginning with a vowel or a diphthong.

Middle/Passive Voice: Endings attached directly to the stem, no thematic vowel (ο/ε) between the stem and the ending. As is the case in the Present Tense.