G'day mmittiga17,

Here's my take on a solution:

#!/usr/bin/env perl -l

use strict;
use warnings;

my %good;

while (<DATA>) {
    my ($id, $flag) = split;
    next unless $id;
    ++$good{$id}[$flag];
}   

for (keys %good) {
    print if $good{$_}[1] && $good{$_}[3];
}   

__DATA__
3-2000/7.48 1
3-2000/7.48 2
3-2000/7.48 2
3-2000/7.48 2
3-2000/7.48 2
3-2000/7.48 2
3-2000/7.48 2
3-2000/7.48 3

4-0000/8.40 2
4-0000/8.40 2
4-0000/8.40 2
4-0000/8.40 2
4-0000/8.40 2
4-0000/8.40 2
4-0000/8.40 3
[download]

Sample run:

$ pm_id_flag_validation.pl
3-2000/7.48
[download]