I see that you have already received good replies. Here is another way to perform this task. The Data::Table module has many useful methods for manipulating tabular data. In this case, the group method is applicable.

The data.tsv file contains the following tab-delimited data

nick    20/5/1950    one
john    18/2/1980    two
nick    19/6/1978    three
nick    20/5/1950    four
nick    12/9/2000    five
john    15/6/1997    six
nick    20/5/1950    seven
[download]

#!/usr/bin/env perl

use strict;
use warnings;

use Data::Table;

# Load input data from tsv file
#   The first argument is the file name
#   The second argument specifies that there is no header row (in this
+ case
#   the Data::Table object that is created will have auto-generated co
+lumn
#   names of col1, col2, etc.
my $dt = Data::Table::fromTSV('data.tsv', 0);

print "The input table is:\n";
print $dt->tsv, "\n\n";

# Group by 'col1' and 'col2'
my $output_t = $dt->group(
    ['col1', 'col2'], # columns to group by
    ['col3'], # Columns to perform calculation on
    [ \&join_vals ], # Apply join_vals function to values found in 'co
+l3' 
    ['values'] # Put the joined values into these columns 
);

print "The output table is:\n";
print $output_t->tsv, "\n\n";

sub join_vals {
  my @data = @_;
  return join("|", @data);
}

exit;
[download]

The input table is:
col1    col2    col3
nick    20/5/1950    one
john    18/2/1980    two
nick    19/6/1978    three
nick    20/5/1950    four
nick    12/9/2000    five
john    15/6/1997    six
nick    20/5/1950    seven


The output table is:
col1    col2    values
nick    20/5/1950    one|four|seven
john    18/2/1980    two
nick    19/6/1978    three
nick    12/9/2000    five
john    15/6/1997    six
[download]