I had a look at the TOML spec. Dictionaries and hash-tables are here called tables. [[mirrors]]
denotes that this in an array of tables.
First, we tried to use multi-dimensional arrays. According to the spec they are fine since we don’t mix different types.
Hugo uses go-toml for parsing. The project’s README states: This library supports TOML version v0.4.0. Looking in the toml spec v0.4.0 we can see that
mirrors = [["dl.site1.com/exe", "Site One"], ["dl.site2.org/exe", "Site2"]]
should work as expected.
Maybe I missed something in between. Nonetheless, the current version is in my eyes more descriptive.