example on matching regex in a variable via case/when/end

case-regex.rb

#!/usr/bin/env ruby

line = "The quick brown fox jumped over the lazy dog"

r = {
  :cat => /cat/,
  :rabbit => /rabbit/,
  :horse => /horse/,
  :dog => /(\w+)\s+dog/
}

case
  when r[:cat].match(line)
    puts "found a cat: #{line}"

  when r[:rabbit].match(line)
    puts "found a rabbit: #{line}"

  when r[:horse].match(line)
    puts "found a horse: #{line}"

  when r[:dog].match(line)
    puts "found a dog: #{line}"
    puts "the word before dog is **#{$~[1]}**"

  else
    puts "did not find any matches: #{line}"
end

__END__

roadrunner:~ oogali$ ./m.rb 
found a dog: The quick brown fox jumped over the lazy dog
the word before dog is **lazy**