test.rb

# encoding: utf-8

require 'rubygems'
require 'benchmark/ips'
require 'set'

TRUE_VALUES = [true, 1, '1', 't', 'T', 'true', 'TRUE'].to_set

def original value
  if value.is_a?(String) && value.empty?
    nil
  else
    TRUE_VALUES.include?(value)
  end
end

def regexp value
  case value
  when String
    value =~ /^(?:1|t(?:rue)?)$/i
  when true, 1
    true
  else
    false
  end
end

n = 50000
Benchmark.ips do |x|
  x.report('original hit') {
    original 'true'
  }

  x.report('original miss') {
    original 'false'
  }

  x.report('regex hit') {
    regexp 'true'
  }

  x.report('regex miss') {
    regexp 'false'
  }
end

__END__
$ ruby test.rb
        original hit   345653.8 (±18.7%) i/s -    1641500 in   4.997906s (cycle=9380)
       original miss   357417.3 (±18.5%) i/s -    1707888 in   5.022346s (cycle=9384)
           regex hit   256663.3 (±27.8%) i/s -    1142302 in   5.040709s (cycle=8218)
          regex miss   349140.4 (±18.6%) i/s -    1665416 in   5.009205s (cycle=9304)