bench.rb

require "benchmark"

Benchmark.bm do |bm|

  string = "1232wrodsfds123123"

  bm.report("named char") do
    10000000.times do
      string =~ /[:digit:]/
    end
  end

  bm.report("old school") do
    10000000.times do
      string =~ /\d/
    end
  end
end

   user     system      total        real

named char 3.810000 0.000000 3.810000 ( 3.804518)
old school 3.650000 0.010000 3.660000 ( 3.651113)