use Modern::Perl;

for ( grep /\S/, <DATA> ) {
	my @data = ( split /\./ )[ 0 .. 3 ];
	splice @data, 1, 1, unpack '(a4)(a2)*', $data[1];
	say "@data";
}

__DATA__
3B40RT.2000033121.7.bin.gz
3B40RT.2000033121.7R.bin.gz
3B40RT.2000033121.7RWER.bin.gz

##</code><code>##

3B40RT 2000 03 31 21 7 bin
3B40RT 2000 03 31 21 7R bin
3B40RT 2000 03 31 21 7RWER bin