Syntax

Regular expressions are written as patterns enclosed within forward slashes. Unlike in Ruby, you cannot specify options or encodings after the final slash, like /node .*/m.

if $host =~ /^www(\d+)\./ {
  notify { "Welcome web server #$1": }
}

Puppet uses Ruby’s standard regular expression implementation to match patterns. Other forms of regular expression quoting, like Ruby’s %r{^www(\d+)\.}, are not allowed. You cannot interpolate variables or expressions into regex values.

If you are matching against a string that contains newlines, use \A and \z instead of ^ and $, which match the beginning and end of a line. This is a common mistake that can cause your regexp to unintentionally match multiline text.

Some places in the language accept both real regex values and stringified regexes — that is, the same pattern quoted as a string instead of surrounded by slashes.