Damien Wyart wrote:
> Many thanks to everyone who responded, the answers are very
> interesting and enlightening !

As far as I can see noone used the Hash with block feature.  So here it
is:

ruby -e 'h=Hash.new(){|ha,l| puts l;ha[l.freeze]=1};ARGF.each {|l| h[l]}'

(David, I'm sorry again this is no #inject solution.)

Kind regards

    robert