my $filename = 'name.20040215135523';

my($tstr) = $filename =~ /\.(\d+)$/;

my(@date) = unpack("A4A2A2A2A2A2", $tstr);

printf("%02d:%02d:%02d %02d.%02d.%04d\n", @date[3,4,5,2,1,0]);