Add Add Comments To Regex With Free-Spacing as a Ruby til

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
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@@ -864,6 +864,7 @@ _1137 TILs and counting..._
 ### Ruby
 
 - [A Shorthand For Rerunning Failed Tests With RSpec](ruby/a-shorthand-for-rerunning-failed-tests-with-rspec.md)
+- [Add Comments To Regex With Free-Spacing](ruby/add-comments-to-regex-with-free-spacing.md)
 - [Add Linux As A Bundler Platform](ruby/add-linux-as-a-bundler-platform.md)
 - [Are They All True?](ruby/are-they-all-true.md)
 - [Assert About An Object's Attributes With RSpec](ruby/assert-about-an-objects-attributes-with-rspec.md)

ruby/add-comments-to-regex-with-free-spacing.md

@@ -0,0 +1,50 @@
+# Add Comments To Regex With Free-Spacing
+
+Ruby's regex syntax supports a [Free-Spacing
+mode](https://ruby-doc.org/core-3.0.1/Regexp.html#class-Regexp-label-Free-Spacing+Mode+and+Comments).
+When this mode is enabled, all the literal whitespace in the regular expression
+is ignored and comments can be included at the end of lines. This is enabled by
+appending the `x` option at the end of the regex.
+
+Here is a regex with Free-Spacing mode enabled (see the `x` at the end).
+
+```ruby
+simple_email = /\A.+@.+\z/x
+```
+
+Though it's enabled, it is not really being used.
+
+Here is the same regular expression, but this time I've spaced it out and added
+comment annotation to make the regex easier to understand.
+
+```ruby
+simple_email = /
+  \A  # beginning of the string
+  .+  # any opening characters
+  @   # the email's `@` symbol
+  .+  # the rest of the email
+  \z  # the end of the string
+/x
+```
+
+To be sure the extra space and comments aren't messing things up, here is some
+code to test it out.
+
+```ruby
+test_emails = [
+  'taco',
+  'email@example.com',
+  'more.complex+email@example.com',
+  '@'
+]
+
+test_emails.each do |email|
+  if (simple_email =~ email) == 0
+    puts "#{email} looks like an email"
+  else
+    puts "#{email} may not be an email"
+  end
+end
+```
+
+[source](https://twitter.com/jasonrudolph/status/1413240725064519681?s=20)