#!/usr/bin/perl

%hash;

while (<DATA>){
        chomp;
        ($key, $value)= split(/[\s+|\t+]/,$_);
        $hash{$key}=$value;
}

foreach $key2 (keys %hash){
        print "$key2 -> $hash{$key2}\n";
}

__DATA__
a       1
a       2
a       1
a       3