Split Ruby regex over multiple lines

Rather than cutting the regex mid-expression, I suggest breaking it into parts:

full_rgx = /This is a message\. A phone number: \d{10}\. A timestamp: \d*?/

msg = /This is a message\./
phone = /A phone number: \d{10}\./
tstamp = /A timestamp: \d*?/

/#{msg} #{phone} #{tstamp}/

I do the same for long strings.

You need to use the /x modifier, which enables free-spacing mode.

In your case:

"bar" =~ /(foo|
           bar)/x

you can use:

"bar" =~ /(?x)foo|
         bar/

Using %r with the x option is the prefered way to do this.

See this example from the github ruby style guide

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

regexp.match? "start groupalt2end"

https://github.com/github/rubocop-github/blob/master/STYLEGUIDE.md#regular-expressions