my $field = "20011023083000";
my $d = qr /(\d\d)/;
my ($year,$month,$day,$hour,$minutes,$seconds) = $field =~ m/(\d{4})$d$d$d$d$d/o;

show();

($year,$month,$day,$hour,$minutes,$seconds) = (localtime)[5,4,3,2,1,0];
$year += 1900;
$month += 1;  # dec = 12 not 11

show();

$string = sprintf "%4d%02d%02d%02d%02d%02d", $year,$month,$day,$hour,$minutes,$seconds;

print "\n\$string $string\n";

sub show {
    print "
    \$year      $year
    \$month     $month
    \$day       $day
    \$hour      $hour
    \$minutes   $minutes
    \$seconds   $seconds
";
}