What would the purpose of switching on and off by alternating the values of $i between 0 and 1 ??, I could not see through it clearly but well, I thought of a simplistic approach guaranteed that your string contains data that can be accommodated uniformly...

#!/usr/local/bin/perl
use strict;
use warnings;

my $hashRef = {};
my $string = "Tom, 18, Jack, 22, Tim, 30";
populateHash($hashRef,$string);

sub populateHash{
        my ($hashRef,$scopedString)  = @_;
        my @stringArray = split (', ',$scopedString);
        %$hashRef = @stringArray;
        return $hashRef;
        }

use Data::Dumper;
print Dumper(\%$hashRef);
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