Before talking about pretérito anterior, there is something that I need to talk about this tense. Although it seems to be used in the past, probably you will not find this structure in writings nor speaking. It has been replaced with the past perfect or preterite. However, I decided to write about it since it is very interesting to see this “weird” verbal tense among many different tenses Spanish has.
Pretérito anterior is used when connecting things that happened in the past with what also had happened in the past. This should be clearer with an example below.
Pretérito anterior is formed preterite form of “haver” + past participle.
Tan pronto como hube terminado la tarea, me acosté.
As soon as I finished homeword, I went to sleep.
These expressions below can evoke pretérito anterior
Así que (-のように)
En cuanto (-の時に、すぐに)
Tan pronto como (すぐに)
Una vez que (一回)