use strict;
use warnings;
use Data::Dump::Streamer;

my @in = (one => 1, two => 2, two => '2.003');
my %hash;

while (@in > 1) {
    my ($key, $value) = splice @in, 0, 2;
    
    push @{$hash{$key}}, $value;
}

Dump \%hash;

##</code><code>##

$HASH1 = {
           one => [ 1 ],
           two => [
                    2,
                    2.003
                  ]
         };