I have found contradicting suggestions for the auxiliary verb to use make the perfect tense of erfahren.
Collins Dictionary (Online) suggests
while de.wiktionary.org suggests
Which is correct?
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In both the meanings to experience something and to get told something, erfahren is used only with haben in the perfect tense. Unlike other verbs like stehen, this is the same throughout the German-speaking countries.
Ich habe gestern erfahren, dass ich heute Dienst habe.
Gestern habe ich die Wirkung einer Absage erfahren.
However, there is also the closely related expression erfahren sein, wherein I would consider erfahren to be an adjectivised present participle rather than a verb. In this expression, erfahren sein means to be experienced. As sein is the full verb here, an phrase such as ‘Ich bin erfahren.’ is actually in present tense and can be transformed into both preterite, perfect and pluperfect separately:
Im Umgang mit dieser Maschine bin ich erfahren.
Er ist im Umgang mit Maschinen sehr erfahren gewesen.
Note that using this expression in the past when referring to a person typically means they passed away — although it could also mean that they’re suffering from severe amnesia or emigrated to Far Far Away.