#!/usr/bin/perl
use strict;
use warnings;


my @b = 1..1000;
my @c = 900..1000;
my @d = 910..1000;
#  my @newb =  grep {$_>850}(@b&&@c&&@d);  ### will not  work!

my %seen;
my @newb = map{ ($_ > 850 and !$seen{$_}++) ?  $_: ()} (@b,@c,@d);

print "@newb\n";