uniq

 The UNIX uniq command drops the duplicate values from it input and prints out the result.
 Usually it is used in a pipe so it receives file rows and prints them on the screen
 (or passes them to the next command in the pipe chain).
 
 In Perl 6 we have a uniq function that receives a list of values and returns 
 the same list after dropping any duplicate value.
 
 "input.txt".slurp.uniq.map:{ "$_\n" }.say  
 
 and this will work once slurp is fixed:
 
 "input.txt".slurp.uniq.say  
 
 will print out the uniq rows in the input.txt file to the screen