Why not do something like this:

# Note: Don't prototype () since that won't let you pass args
sub builder {
    my $data = shift;                       # $i in your code I'm keep
+ing in @_

    my %hash = ();
    my $ptr = \%hash;                       # Set up a pointer to %has
+h

    for (my $cur = 0; $cur < $#_; $cur++) {
        $ptr->{$_[$cur]} = {};              # Manipulate using our poi
+nter
        $ptr = $ptr->{$_[$cur]};            # and advance it as we go
    }

    $ptr->{$_[$#_]} = $data;                # Do our last hash
    return %hash;                           # and do what you want wit
+h %hash
}

my %hash = builder('abcde', 'a', 'b', 3);
print $hash{'a'}{'b'}{3};                   # 'abcde'
[download]

I used @_ instead of your $i reference, but change things around if you really need it that way. The idea's the same. Perhaps there's a more elegant solution but I couldn't see one at the moment. Have fun.