html_safe gotcha

gistfile1.rb

#
# This is pretty confusing until you know what's going on...
#
# See http://techspry.com/ruby_and_rails/html_safe-and-helpers-in-rails-3-mystery-solved/
# for an explanation...
#
ruby-1.8.7-p334 :025 > foo_safe = "<p>foo</p>".html_safe
 => "<p>foo</p>" 

ruby-1.8.7-p334 :026 > (foo_safe + "<p>bar</p>").html_safe # not what you thought! unintuitive!
 => "<p>foo</p>&lt;p&gt;bar&lt;/p&gt;" 

ruby-1.8.7-p334 :027 > "#{foo_safe}<p>bar</p>".html_safe # I think it works because of the implicit to_s
 => "<p>foo</p><p>bar</p>"

ruby-1.8.7-p334 :028 > foo_safe.safe_concat("<p>bar</p>") # correct, but looks pretty clunky, right?
 => "<p>foo</p><p>bar</p>"