In Perl, "." is the concatenation operator.

In regex patterns, it's the "match (almost) any characters" atom.

In character classes, it's a period.

All of these are wise choices. Just like it wouldn't make sense for "." to mean concatenation inside of regexp patterns, it wouldn't makes sense for "." to mean "any character" inside of a character class. (e.g. [.abc] would be the same as just .)

It didn't lose any special meaning, it wasn't given any special meaning.