my $t="20070716194009";

my ($time) = $t =~ s/(\d{4})(\d{2})(\d{2})(\d{2})(\d{2})(\d{2})/$3.$2.$1 $4:$5:$6/;

print "$time\n";

#!/usr/bin/perl

use strict;
use warnings;

my $t = '20070716194009';

$t =~ s/(\d{4})(\d{2})(\d{2})(\d{2})(\d{2})(\d{2})/$3.$2.$1 $4:$5:$6/;

print $t;

(my $time = $t) =~ s/(\d{4})(\d{2})(\d{2})(\d{2})(\d{2})(\d{2})/$3.$2.$1 $4:$5:$6/;