gistfile1.txt

$ facter | grep puppet
puppetversion => 2.6.1
$ cat lib/puppet/parser/functions/array_del.rb 
Puppet::Parser::Functions::newfunction(
  :array_del,
  :type => :rvalue,
  :doc => "Deletes items from an array

    Example: array_del(['a','b'],'b') -> ['a']"
) do |args|
  raise Puppet::ParseError, 'array_del() needs two arguments' if args.length != 2
  args[0].to_a.delete(args[1])
  args[0]
end
$ cat test.pp 
$a = ['a','b','c']

$b = array_del($a,'b')
notice $b
notice $a
$ RUBYLIB=lib/ puppet test.pp 
notice: Scope(Class[main]): a c
notice: Scope(Class[main]): a c