For focused advice you need to give us the bigger picture. If the search is occasional or the array is small (supply your own definition for both those) then grep is the tool of choice. If you don't care about the original order of the data and the data set is of modest size (again supply your own definition) then a hash of arrays may be appropriate. If the data size is modest (ditto) but you need order information add an ordinal along with the data value for each item (see below). If the data is large, use a database.

For the penultimate option consider:

use strict;
use warnings;

my $entries = 0;
my %data;

while (<DATA>) {
    chomp;
    my ($name, $value) = split ' ', $_, 2;

    push @{$data{$name}}, [$entries++, $value];
}

for my $name (sort keys %data) {
    print "$name\n";
    print "   $_->[1]\n" for sort {$a->[0] <=> $b->[0]} @{$data{$name}
+};
}

__DATA__
Jim     12
John    15
Peter   08
Andrew  34
Jim     57
Andreas 27
[download]

Prints:

Andreas
   27
Andrew
   34
Jim
   12
   57
John
   15
Peter
   08
[download]