Swedish, like English, is a Germanic language. The Germanic languages derive from a common ancestor, proto-Germanic, which is thought to date from around 500 BCE. By around 200 CE, proto-Germanic had split into three branches: West Germanic (now English, German, Dutch, Frisian), North Germanic (now Swedish, Norwegian, Danish, Icelandic, Faroese), and East Germanic (eg Gothic; now all extinct).
One feature of Germanic languages is the presence of a class of verbs (so-called weak verbs) that form the past tense by addition of a dental suffix (d or t), as opposed to strong verbs, which have a change in vowel sound to indicate past tense:
Jag arbetar. I work.
Jag arbetade. I worked.
Jag har arbetat. I have worked.
Contrast:
Jag dricker. I drink.
Jag drack. I drank.
Jag har druckit. I have drunk.
Note that in English, the two past tense forms of weak verbs are identical and end in d, whereas in Swedish the simple past tense has a d, but the supine has a t. One exception is the class 2b verbs, such as köpa, to buy, which have a simple past tense form with t:
Jag köper. I buy.
Jag köpte. I bought.
Jag har köpt. I have bought.
In English, the following is quite ungrammatical to me, although it may be OK in some dialects (as it is obvious what meaning is intended)?:
*I seen a lot of movies.
And so I thought something similar would be true in Swedish, which was why I suspected a typo when I read (something like) the following:
… för dig som provat på orientering tidigare …
… for you who already tried orienteering…
That is, the bare supine form of the verb prova, where I was expecting har provat. But after trying to learn all these grammar rules, a colleague tells me this is quite acceptable in spoken Swedish, and even passable in written Swedish, so *sigh*.