## function

module Puppet::Parser::Functions
   newfunction(:lookupvar, :type => :rvalue) do |args|
      if lookupvar(args[0]) {
         return lookupvar(args[0])
      } else {
         return undef
      }
      end
end

## output

root@pinocchio:~# puppetd -vt --noop
info: Loading fact localuidgid
info: Retrieving facts
info: Loading fact localuidgid
err: Could not retrieve catalog: Uncaught exception /usr/lib/ruby/1.8/puppet/parser/functions/lookupvar.rb:3: syntax error, unexpected '{', expecting kTHEN or ':' or '\n' or ';'
/usr/lib/ruby/1.8/puppet/parser/functions/lookupvar.rb:5: syntax error, unexpected '}', expecting kEND
      } else {
       ^
/usr/lib/ruby/1.8/puppet/parser/functions/lookupvar.rb:6: void value expression
/usr/lib/ruby/1.8/puppet/parser/functions/lookupvar.rb:6: odd number list for Hash in method puppetmaster.getconfig
warning: Not using cache on failed catalog