# development environment (Rails 3.0.0.beta1)
a = ["a".html_safe, "b".html_safe]
b = a + ["c"]
puts a.join(" ".html_safe).html_safe?
# prints false
puts a.each_with_index.inject("".html_safe) { |a, elem| if elem[1] > 0; a << " ".html_safe; end; a << elem[0] }.html_safe?
# prints true
puts b.each_with_index.inject("".html_safe) { |a, elem| if elem[1] > 0; a << " ".html_safe; end; a << elem[0] }.html_safe?
# prints true!