How does Icelandic express present and perfect aspects?

In Icelandic, the present and perfect aspects are expressed through specific periphrastic constructions rather than simple verb inflections.1

• Present aspect: This is expressed using the construction er að followed by the infinitive (e.g., er að ganga, meaning "is going").1
• Perfect aspect: This is expressed using the construction er búinn að followed by the infinitive, which literally translates to "is through [doing]" (e.g., er búinn að ganga, meaning "is through going").1

These specialized constructions allow Icelandic to convey these aspects distinctly, differing from the methods used in other Scandinavian languages, which often rely on different auxiliary combinations or positional verbs to indicate similar meanings.1