Perfect.—For the simple perfect and pluperfect periphrastic forms are often used.
a. For the perfect or pluperfect active indicative the forms of the perfect active participle and εἰμί or ἦν may be used: as λελυκώς εἰμι for λέλυκα, λελυκὼς ἦν for ἐλελύκη. So βεβοηθηκότες ἦσαν for ἐβεβοηθήκεσαν (βοηθέω
b. For the perfect active a periphrasis of the aorist participle and ἔχω is sometimes used, especially when a perfect active form with transitive meaning is lacking; as στήσα_ς ἔχω
c. In the perfect active subjunctive and optative the forms in -κω and -κοιμι are very rare. In their place the perfect active participle with ὦ and εἴην is usually employed: λελυκὼς (λελοιπὼς) ὦ, εἴην. Other forms than 3 sing. and 3 pl. are rare. Cp. cross691, cross694.
d. The perfect or pluperfect passive is often paraphrased by the perfect participle and ἐστί or ἦν; as γεγραμμένον ἐστί
e. In the third plural of the perfect and pluperfect middle (passive) the perfect middle participle with εἰσί (ἦσαν) is used when a stem ending in a consonant would come in direct contact with the endings -νται, -ντο. See cross408.
f. The perfect subjunctive and optative middle are formed by the perfect middle participle with ὦ or εἴην: λελυμένος ὦ, εἴην.
g. The perfect imperative of all voices may be expressed by combining the perfect participle with ἴσθι, ἔστω ( cross697). λελυκὼς ἴσθι
h. Periphrasis of the infinitive is rare:
Future Perfect Active.—The future perfect active of most verbs is formed by combining the perfect active participle with ἔσομαι
a. The perfect middle participle is used in the case of deponent verbs: ἀπολελογημένος ἔσομαι
Future Perfect Passive.—The future perfect passive may be expressed by using the perfect middle (passive) participle with ἔσομαι
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].