index   @ar_1   @ar2
0       John    London
1       Mike    Paris
2       Vivien  Milan
3       John    Berlin
4       Vivien  Paris
etc...


##</code><code>##

John   => [London, Berlin],
Mike   => [Paris],
Vivien => [Milan, Paris]


##</code><code>##

use strict;
use Data::Dump qw/dump/;

my @ar_1 = qw/John Mike Vivien John Vivien/;
my @ar_2 = qw/London Paris Milan Berlin Paris/;

my %hash;

foreach (0 .. $#ar_1) {
    push @{$hash{$ar_1[$_]}}, $ar_2[$_];
}

print dump(\%hash);