my $in = [ one => 1, two => 2, two => '2.003' ];
my %h;

for @$in -> $k, $v {
    %h{$k}.push: $v;
}

##</code><code>##

use v6;

my $in = [ 'one', 1, 'two', 2, 'two', '2.003' ];
my %h;

for @($in) -> $k, $v {
    if %h{$k} {
        %h{$k}.push: $v;
    } else {
        %h{$k} = [ $v ];
    }
}

say %h.perl;

# output:
# {"one" => [1], "two" => [2, "2.003"]}

##</code><code>##

use v6;

my $in = [ one => 1, two => 2, two => '2.003' ];
my %h;

for @($in) {
    if %h{.key} {
        %h{.key}.push: .value;
    } else {
        %h{.key} = [ .value ];
    }
}

say %h.perl;

# vim: ft=perl6 sw=4 ts=4 expandtab
# same output

##</code><code>##

%h{.key}.push: .value for @$in:

##</code><code>##

my %h = $in.classify: { $_ };

##</code><code>##

for @($in) -> $k, $v {
    %h{$k} //= [];
    %h{$k}.push: $v;
}