https://twitter.com/tadsan/status/1734383869196161525

benchmark_string_replace.rb

require "bundler/inline"

gemfile do
  source "https://rubygems.org"
  gem "benchmark-ips"
end

I = "Rubyist"
PHPER = "PHPer"

puts RUBY_DESCRIPTION
puts ""

Benchmark.ips do |x|
  x.report("String#replace") { I.replace PHPER }
  x.report("String#gsub!") { I.gsub!(I, PHPER) }
  x.report("String#[]=") { I[0..-1] = PHPER }
end

result.txt

ruby 3.3.0rc1 (2023-12-11 master a49643340e) [arm64-darwin23]

Warming up --------------------------------------
      String#replace     2.298M i/100ms
        String#gsub!   384.013k i/100ms
          String#[]=     1.599M i/100ms
Calculating -------------------------------------
      String#replace     23.031M (± 0.3%) i/s -    117.219M in   5.089779s
        String#gsub!      3.851M (± 0.6%) i/s -     19.585M in   5.085532s
          String#[]=     16.063M (± 0.4%) i/s -     81.545M in   5.076715s