Is the order of the lines meaningfull?
If not you could use a hash which holds an array with all the values:

my %people;
while( my $line = <IN> ) {
    my ($name, $value) = split /\s+/, $line;
    if (!exists $people{$name}) {
        $people{$name} = [ $value ]; # store array with one value
    }
    else {
        push @{$people{$name}}, $value; # push 2nd,3rd,.. value on arr
+ay
    }
}
[download]

The %people hash would then look like:

%people = (
          'Andreas' => [
                         '27'
                       ],
          'John' => [
                      '15'
                    ],
          'Andrew' => [
                        '34'
                      ],
          'Jim' => [
                     '12',
                     '57'
                   ],
          'Peter' => [
                       '08'
                     ]
        );
[download]

This preserves the order of the values but not the order of the names.