#!/usr/bin/perl

use strict;
use warnings;

while(<DATA>) {
  chomp(my $is_valid = $_);
  print $is_valid, "\n" if grep {/^$is_valid$/} (1950..2050);
}

__DATA__
1949
1950
1951
1999
2000
2001
2010
2049
2050
2051
2102
22102
19534
19080
20010