In this tense the auxiliary verb “haber” is used in the preterit tense with the past participle. It is rarely used in speech. It can be thought of as a feature of formal literary Spanish. It is usually used after: apenas (barely), despues de que (after), cuando (when), enseguida que (soon after), en cuanto (all of a sudden), tan pronto como (as soon as), una vez que (once).
yo hube hablado
I had talked
tú hubiste hablado
you had talked
él/ella/usted hubo hablado
he/she/you had talked
nosotros hubimos hablado
we had talked
vosotros hubisteis hablado
you had talked
ellos/ellas/ustedes hubieron hablado
they/you had talked
yo hube servido
I had served
tú hubiste servido
you had served
él/ella/usted hubo servido
he/she/you had served
nosotros hubimos servido
we had served
vosotros hubisteis servido
you had served
ellos/ellas/ustedes hubieron servido
they/you had served
- Apenas hubo llegado, y se fue. (He had just arrived when he left.)