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

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)