gistfile1.txt

#!/usr/bin/env ruby

str = 'one two three'

str = str.gsub(/t/) do |match|
  match = 'X'
end

puts str

gistfile2.txt

rubocop test.rb
Inspecting 1 file
W

Offenses:

test.rb:5:25: W: Unused block argument - match. You can omit the argument if you don't care about it.
str = str.gsub(/t/) do |match|
                        ^^^^^
test.rb:6:3: W: Useless assignment to variable - match.
  match = 'X'
  ^^^^^

1 file inspected, 2 offenses detected