irb(main):053:0> YAML.load(Regexp::Raw.new('x','s').to_yaml)
Traceback (most recent call last):
       16: from (irb):53
       15: from /home/w/.rbenv/versions/2.7.1/lib/ruby/2.7.0/psych.rb:279:in `load'
       14: from /home/w/.rbenv/versions/2.7.1/lib/ruby/2.7.0/psych/nodes/node.rb:50:in `to_ruby'
       13: from /home/w/.rbenv/versions/2.7.1/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:32:in `accept'
       12: from /home/w/.rbenv/versions/2.7.1/lib/ruby/2.7.0/psych/visitors/visitor.rb:6:in `accept'
       11: from /home/w/.rbenv/versions/2.7.1/lib/ruby/2.7.0/psych/visitors/visitor.rb:16:in `visit'
       10: from /home/w/.rbenv/versions/2.7.1/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:313:in `visit_Psych_Nodes_Document'
        9: from /home/w/.rbenv/versions/2.7.1/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:32:in `accept'
        8: from /home/w/.rbenv/versions/2.7.1/lib/ruby/2.7.0/psych/visitors/visitor.rb:6:in `accept'
        7: from /home/w/.rbenv/versions/2.7.1/lib/ruby/2.7.0/psych/visitors/visitor.rb:16:in `visit'
        6: from /home/w/.rbenv/versions/2.7.1/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:208:in `visit_Psych_Nodes_Mapping'
        5: from /home/w/.rbenv/versions/2.7.1/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:394:in `revive'
        4: from /home/w/.rbenv/versions/2.7.1/lib/ruby/2.7.0/psych/visitors/to_ruby.rb:401:in `init_with'
        3: from /home/w/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/bson-4.9.0/lib/bson/regexp.rb:168:in `respond_to?'
        2: from /home/w/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/bson-4.9.0/lib/bson/regexp.rb:140:in `compile'
        1: from /home/w/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/bson-4.9.0/lib/bson/regexp.rb:253:in `options_to_int'
NoMethodError (undefined method `include?' for nil:NilClass)