Common tasks in Perl 6

From Ajswiki

Common tasks in Perl 6 is an overview of some of the most oft-performed tasks in Perl programming language, version 5, re-cast in Perl 6 syntax. This is intended to help newcomers to Perl 6 development get their feet.

Making things unique

In Perl 5, I often write:

foreach (@x) {
 push @y, $_ unless $seen{$_}++;
}

This creates a new list y which contains all of the elements of x that were unique, preserving original order. In Perl 6, this is:

for @x {
 push @y, $_ unless %seen{$_}++;
}

As you can see, it looks almost exactly the same. However, you can also name that loop variable with ease, and probably should:

for @x -> $item {
 push @y, $item unless %seen{$item}++;
}

Junctions

Junctions are multiple values represented in a single expression or variable. They are aggregated with some logical operation (and/or) and can be negative as well. Here are some examples:

if $x == any(1,2,3) { ... } # Only if $x is 1, 2 or 3
all($x,$y,$z).say; # Call the say method on all three
if $x < all(@y) { ... } # only if $x is less than all values in @y

URL encoding

I very often use this Perl 5 code to transform strings into valid URL query components:

s/([^\w._-])/sprintf "%%%02x", $1/eg;

In Perl 6, that's:

s:g /<-[\w._-]>/{sprintf "%%%02x", $1}/;

Or, if we assume a URI module:

s:g /<-URI.valid_querychars>/{sprintf "%%%02x", $1}/;

... TBD ...