use strict;
use warnings;

my %hash = (
  one => [1,2,4],
  two => [5,7,9],
);
my @new1 = (10,11,12);
my $new2 = [13,14,15];

push(@{$hash{one}}, @new1);
push(@{$hash{one}}, @$new2);
push(@{$hash{one}}, 16, 17, 18);

print join(',', @{$hash{one}});