blank_bench.rb

# gem install 'benchmark-ips'

require 'benchmark/ips'

long = ' ' * 1_000_000 + 'x'
REGEXP = /\A[[:space:]]*\z/

['      ', 'hello', long].each do |str|
  Benchmark.ips do |x|
    x.report('with_regexp') { REGEXP.match? str }
    x.report('with_lstrip') { str.lstrip.empty? }
    x.compare!
  end
end