Misleading heredoc can fool even expert ruby coders

innocent_looking_file.rb

EOF = 0
def grocery(list)
  puts "We've stolen #{list}"
end

def list
  "your credit card"
end

string_heredoc.rb

string = string
string <<EOF
  grocery list
EOF

puts string.inspect

string_heredoc_output.txt

$ ruby string_heredoc.rb
We've stolen your credit card
"\000"

syntax_error.txt

$ ruby string_heredoc.rb
string_heredoc.rb:12: uninitialized constant EOF (NameError)