I don't know why, but this is a part of the language's syntax, for example when matching a union type each named variant also has that period. Same with the argument for print statements (`print("{s}", .{var})`).

I think it allows the parser to be context-free since otherwise it is tricky to distinguish it from a code block. They could have picked a different sigil, but I think . was landed on because it had the fewest semantic conflicts with other concepts in the language (for example % is used to denote modular arithmetic)

In zig code blocks are expressions and can appear in a lot of places, e.g. on the RHS of an assignment. Probably possible to not need the dot but considerably more complicated.