#!/usr/bin/env perl
use strict;
use warnings;
my %hash;
for(qw/1689 9679 6978 2792 2514 5472 1520 9342 5544 1268 0165 1979 7314 2101 7221 
+9539 3882 1812/) {
  $hash{$_}++;
}
my $tested = '2101';
if( exists $hash{$tested} ) {
    print "OK";
}
else {
    print "Not there";
}