#!/usr/bin/env perl -l

use strict;
use warnings;

my $first;

print join ' ' => @$_ for
    grep { $_->[-1] - $first <= 500 }
    sort { $b->[-1] <=> $a->[-1] }
    map { $first = $_->[-1] unless $first; $_ }
    map { [ split ] } <DATA>;

__DATA__
ID1 ch1 70 mir abc xyz ch2 2050
ID4 ch1 120 mir abc xyz ch2 2025
ID2 ch1 90 mir abc xyz ch2 4000
ID3 ch1 100 mir abc xyz ch2 2045