#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

*ARGV = *DATA{IO} unless @ARGV;

my (%all, %duplicates);
<>;  # Skip header.
while (<>) {
    my ($id, $type, $pos) = split;
    undef @{ $duplicates{$type}{$pos} }{ $id, $all{$type}{$pos} }
        if exists $all{$type}{$pos};
    $all{$type}{$pos} = $id;
}

say join ' ', 'Duplicates:',
    join '; ',
    map { join ', ', map keys %$_, values %$_ }
    values %duplicates;

__DATA__
ID   Type Pos
1    1    10
2    1    11
3    1    11
4    1    15
5    2    5
6    2    5
7    2    7
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($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
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