use IO::YAML;
my $yaml_fh = IO::YAML->new(
    handle => \*DATA,
    mode => '<',
    auto_load => 0,
    )
        or die "Can't open ...: $!";

while ( not $yaml_fh->eof ) {
    my $yaml = <$yaml_fh>;
    
    # Skip comment-only blocks. Is it a bug that this ever happens?
    next if /\A(?:^#[^\n]*\n)+\z/m;
}
__DATA__
# this is a comment about the 40MB of YAML documents to follow
---
foo: 1
bar: 2