The Swedish perfect tense: har ätit, har bott, har varit

The Swedish perfect tense is har plus a special verb form called the supine: Jag har ätit, I have eaten. It covers experiences, results, and things that started in the past and are still going. Most of it maps comfortably onto English "have done". The interesting ten percent, where the two languages part ways, is at the end of this article, and it's worth the trip.

Building it: har + supinum

The supine (supinum) is a form Swedish keeps exclusively for this job. By verb group, matching the groups from the preteritum article:

group	infinitive	preteritum	supinum	perfect
1	tala	talade	talat	har talat
2	läsa	läste	läst	har läst
3	bo	bodde	bott	har bott
4	äta	åt	ätit	har ätit
4	dricka	drack	druckit	har druckit

The endings: group 1 takes -at, group 2 takes -t, group 3 takes -tt, and the strong group 4 takes -it. The everyday irregulars, worth learning as a set: varit (been), haft (had), gjort (done), sagt (said), sett (seen), fått (gotten), gått (gone), kommit (come).

As always in Swedish: no person endings anywhere. And note what Swedish does not do: no "is gone"-style choices between have and be. It is always har.

What the perfect is for

Experience, with no particular time attached: Jag har varit i Sverige tre gånger. I've been to Sweden three times.
A result that matters now: Hon har köpt en ny cykel. She has bought a new bike (and has it now).
Something that started in the past and continues: Jag har bott här i två år. I've lived here for two years, and still do.

Negations and words like aldrig (never) slot in between har and the supine: Vi har aldrig varit i Kiruna. We've never been to Kiruna.

Perfekt or preteritum: the actual rule

Here is the boundary, and it's cleaner than most textbooks make it sound:

The moment you name a finished time, Swedish switches to preteritum. Yesterday, last week, in 2019, when I was a child: I går åt jag pizza. Never "i går har jag ätit". If your language builds its spoken past with "have" (German, French, Italian), this is the habit to unlearn in Swedish.
No stated time, and the door is still open? Perfect. Har du ätit frukost? Have you had breakfast (this morning, which is still happening)?

The pair that shows the whole system in one short sentence each:

Jag har bott i Umeå i två år. I've lived in Umeå for two years. You still live there.
Jag bodde i Umeå i två år. I lived in Umeå for two years. You've moved; that chapter is closed.

Same verb, same time span. The tense alone tells a Swede whether you're still there. That's not bookkeeping, that's meaning, and it's why this distinction rewards the effort.

Hear the perfect

Five sentences across all its jobs.

Swedish

Jag har bott i Sverige i två år.

Har du ätit frukost?

Vi har aldrig varit i Kiruna.

Hon har köpt en ny cykel.

Jag har läst boken två gånger.

English

I have lived in Sweden for two years.

Have you eaten breakfast?

We have never been to Kiruna.

She has bought a new bike.

I have read the book twice.