Hello Monks!
I am trying to think of how to implement the following:
My task is, if I have a tab-separated file, like the following example lines:
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]
How would I group the lines using BOTH name & date as "key", i.e. the output would be:
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]

because nick, on 20/5/1950 has 3 measurements.
I know how I would group only using the name:
use strict;
use warnings;

my %res;
while (<>) 
{
    my ( $name, $rest ) = split /\t/;
    push @{ $res{$name} }, $rest;
}
for ( sort keys %res ) {
    print "$_ ", join( "|", @{ $res{$_} } ), "\n";
}

[download]

but now I need to also take the date into account. Can you help me?

In reply to which data structure do I need for this grouping problem? by Anonymous Monk

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