The present perfect subjunctive is formed using the formula below:

present subjunctive conjugation of haber + the past participle = present perfect subjunctive

The table below shows the present subjunctive conjugation of the helping verb haber.

yo	haya
tú	hayas
Ud./él/ella	haya
nosotros (as)	hayamos
vosotros (as)	hayáis
Uds./ellos/ ellas	hayan

The past participle of ver (to see) is irregular - visto.

Below are examples of the present perfect subjunctive. Note that there are two possible English translations for each example.

haya visto - I saw (or) I have seen

hayas visto - you saw (or) you have seen

hayamos visto - we saw (or) we have seen

The present perfect subjunctive is used in the same types of clauses as the present subjunctive, and normally is used: to indicate the action as completed with governing verbs in the present or future tense or command forms. Let's look at some example sentences:

Por muchas que hayas visto, debes ir a ver ésta.
However many you've seen, you should go and see this one (film).

Tal vez no se haya ido.
Perhaps he/she has not left.

Es improbable que no se haya dado cuenta.
It's unlikely that he/she has not realized it.

Ha robado mi monedero sin que yo me haya dado cuenta.
He/she had stolen my change purse without me having realized it.

No hay nadie que lo haya visto.
No one has seen it.

Prefiero que me lo hayas dicho.
I prefer that you have told me it.