ruby 2.3.1

regexen.rb

require 'benchmark'

n = 5_000_000

Benchmark.bmbm do |x|
  x.report('String#match') do
    n.times do
      'metadata:foo=bar'.match(/metadata:/)
    end
  end
  x.report('String#=~') do
    n.times do
      'metadata:foo=bar' =~ /metadata:/
    end
  end
  x.report('String#start_with?') do
    n.times do
      'metadata:foo=bar'.start_with? 'metadata:'
    end
  end
end

# Rehearsal ------------------------------------------------------
# String#match         5.010000   0.010000   5.020000 (  5.031097)
# String#=~            1.460000   0.000000   1.460000 (  1.461489)
# String#start_with?   0.680000   0.000000   0.680000 (  0.694000)
# --------------------------------------------- total: 7.160000sec

#                          user     system      total        real
# String#match         4.960000   0.010000   4.970000 (  4.975006)
# String#=~            1.420000   0.000000   1.420000 (  1.423937)
# String#start_with?   0.640000   0.000000   0.640000 (  0.641189)