You can split on the full-stops (which are regular expression metacharacters so need to be escaped) but use capturing parentheses in the regex so that they are retained in the resulting array; (have a look at perlretut, perlreref and perlre). Then you can construct your new string by interpolating array slices (Slices) in a double-quoted string, first having set the list separator (see $LIST_SEPARATOR in perlvar) to an empty string so that each element abuts the next.

$ 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]
$
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I hope this is helpful.