The following two hints are taken from Github's Ruby style guide Show archive.org snapshot :

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Read more Show archive.org snapshot

If your regular expression mentions a lot of forward slashes, you can use the alternative delimiters %r(...), %r[...] or %r{...} instead of /.../.

 %r(/blog/2011/(.*))
 %r{/blog/2011/(.*)}
 %r[/blog/2011/(.*)]

If your regular expression is growing complex, you can use the /x modifier to ignore whitespace and comments or use named groups or Regexp.union Show archive.org snapshot :

regexp = %r{
  start         # some text
  \s            # white space char
  (group)       # first group
  (?:alt1|alt2) # some alternation
  end
}x

If you would like to match whitespace characters, you have to escape them if they are not contained in a character class.