use strict;
my @ar1=qw/1 2 2 3 3 3 4 4 4 4/;
my @ar2=qw/1 2 3 4/;
my %ar2;
$ar2{$_} ++ for @ar2;
my @ar3 = grep {not($ar2{$_} and $ar2{$_}--)} @ar1;
print "$_\n" for @ar3;