From: Paul McMahon <pm@...>
Date: 2007-10-22T10:35:32+09:00
Subject: Re: gsub does not work with do/end block, only brackets

Braces have high precedence, do end has low precedence so with

puts "abcdefg".gsub(/abc/) do |x|
   x.upcase
end

puts is being passed the block, whereas in

puts "abcdefg".gsub(/abc/) { |x|
   x.upcase
}

gsub is being passed the block.  If you want to use do end, you can do  
something like

puts("abcdefg".gsub(/abc/) do |x|
   x.upcase
end)

or

s = "abcdefg".gsub(/abc/) do |x|
   x.upcase
end
puts s