$ perl -E '
> $text = q{this.is.example.text};
> @items = split m{(\.)}, $text;
> say for @items;
> $new = do                 
>    {
>        local $" = q{};
>        qq{[@items[ 0 .. 3 ]] [@items[ 4 .. 6 ]]};
>    };
> say $new;'
this
.
is
.
example
.
text
[this.is.] [example.text]
$