Raku (formerly Perl6) is a a really cool language I've been using rakubrew

Here are some examples of features the actual source code can be found bellow in an order other than that which I expound them: 

here is a hello world program that pauses for input at the end.


#!/usr/bin/env raku

use v6;

my $msg = "Howdy";

say "$msg Cowboy";

say $*IN.get;

say $*IN.lines(1);

This will actually pause for two lines of input and write both of them out. I did this to show the two ways I've found to get input form stdin now called $*IN. the program actually says "Howdy Cowboy" rather than "Hello World" but since when have I been traditional. and here is another example: 



unit module Fact;

multi sub postfix:<!>(Int $n) is export {

     [*] 1..$n;


sub prefix:<√>(Num $n) is export {

    return sqrt($n);


sub infix:<.oO>($name, $thought) is export {  

    say "$name thinks $thought"


sub infix:<+->($a, $b) is export { ($a - $b) .. ($a + $b) }


Note the parameters are typed also note I'm defining new operators including a postfix ! for factorial,  here is an example of them in use.


#!/usr/bin/env  raku

use v6;

use Fact;

say 0!;

say 1!;

say 6!;

say 10!;

say √ 64.Num;

say √√√256.Num;

"grizzly" .oO "Perl 6 is cool";

say 2.78  ~~ 10 +- 3 ?? 't' !! 'f';     # f

say 7.5   ~~ 10 +- 3 ?? 't' !! 'f';     # t

say 13    ~~ 10 +- 3 ?? 't' !! 'f';     # t

say 13.1  ~~ 10 +- 3 ?? 't' !! 'f';     # f

Note the cast to turn Ints into Nums I shouldn't have to do this but Rakudo cannot seam to work out that Ints and Rats are Nums I'm using the current Trunk version from github to get (git clone git://github.com/rakudo/rakudo.git), Niecza cannot handle the postfix ! it lets you define this, but when you use it it thinks a prefix not ! is being abused.

here are some more examples:


#!/usr/bin/env raku

use v6;

for @*ARGS -> $arg {

    my Num  $target = $arg.Num;

    my Num  $guess  = $target;

    while (abs( $guess**2 - $target ) > 0.000000000000000005) {

        $guess += ( $target - $guess**2 ) / ( 2 * $guess );

        say $guess;


    say '=' x 80;


This shows how you can type variables it also shows the new @*ARGS array which replaces @ARGV as ARGV  is really quite cryptic sorry C guys.  

here is cat using the Shell::Command module  from the File::Tools library,  (see the Libraries page)


#!/usr/bin/env raku

use v6;

use Shell::Command;



for @*ARGS -> $arg {

    given open($arg) {

        for .lines -> $line {

            say $line;






Note | is the flatten operator now bitwise or is +| for numeric and ~| for string bitwise or also note +& is numeric bitwise and and ~& for string bitwise and. 

Also note the #`« … » multi-line comment around the alternate implementation, you can use #`( … ) or substitute any number of [ or { followed by the same number of closing brackets or braces or parenthesis or use as many French quotes as you like « and athe same number of closing French quotes » so #`(((( some stuff 

on multiple 

lines ))))

some more stuff can 

is  a valid comment. 

here are some links for further reading