Everyone has put in their ways, I'll put mine too for consideration... :)

#!/usr/bin/perl

use strict;
use warnings;

my $str1 = "1,2,3";
my $str2 = "a,b,c";

my ($k, %hash, $i);
$i = 0;

my @keys = split /,/, $str1;
my @values = split /,/, $str2;

foreach $k (@keys){
    $hash{$k} = $values[$i++];
}

print %hash;
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I leave it up to you to print the hash in the formatted way