require 'better-benchmark'
 
b = 'b'
r = /a#{b}/
s = 'ab'
 
puts "Precreated interpolated vs. not precreated interpolated"
 
result = Benchmark.compare_realtime(
  :iterations => 10,
  :inner_iterations => 1_000_000,
  :verbose => true
) { |iteration|
  r =~ s
}.with { |iteration|
  /a#{b}/ =~ s
}
 
Benchmark.report_on result
 
 
# % ruby19 regexp-bench3.rb
# Precreated interpolated vs. not precreated interpolated
# ..........
# Set 1 mean: 1.125 s
# Set 1 std dev: 0.022
# Set 2 mean: 7.795 s
# Set 2 std dev: 0.074
# p.value: 1.0825088224469e-05
# W: 0.0
# The difference (+593.2%) IS statistically significant.