Store the raw data in an array of arrays. Store the duplicate information in a hash. Combine type and position to form a single key. The value is a reference to an array of indicies into the raw data.

use strict;
use warnings;
my @raw_data;
my %dups;
my $i = -1;
<DATA>; # skip header
while (my $line = <DATA>) {
    my ($id, $type, $pos) = split /\s+/, $line;
    $raw_data[++$i] = [$id, $type, $pos];
    my $key = "$type:$pos";
    $dups{$key} = []  if !exists $dups{$key};
    push @{$dups{$key}}, $i;
}
foreach my $entry (@raw_data) {
    my $key = "$entry->[1]:$entry->[2]";
    print "@$entry\n" if (@{$dups{$key}} > 1);
}
__DATA__
ID   Type Pos
1    1    10
2    1    11
3    1    11
4    1    15
5    2    5
6    2    5


OUTPUT:
2 1 11
3 1 11
5 2 5
6 2 5
[download]

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.