ts <decoux / moulon.inra.fr> writes:
>  Ruby has really a problem with 'duplicate'. I must say that I've found
>  very strange the rules used by the regexp engine in this case.
> 
>  Another example
> 
> pigeon% ruby -e 'puts "OK" if /(a)*-\1b/ =~ "aaa-b"'
> OK
> pigeon% 
> 
> Guy Decoux

Certainly it is a problem. Try the following:

[0]> ruby -e 'puts "OK" if /(a)+-\1b/ =~ "aaa-b"'
[0]>

--Leo--