use Data::Dumper;

my @start = (
    [qw( a b c )],
    [qw( a b d )],
    [qw( b b b )],
);
my %finish;
my $e = join '', map {
    join '', '$finish', ( map {qq{{'$_'}}} @$_ ), " = 1;\n"
} @start;

print $e, "\n";
eval $e;

print Dumper \%finish;
__END__
$finish{'a'}{'b'}{'c'} = 1;
$finish{'a'}{'b'}{'d'} = 1;
$finish{'b'}{'b'}{'b'} = 1;

$VAR1 = {
          'a' => {
                   'b' => {
                            'c' => 1,
                            'd' => 1
                          }
                 },
          'b' => {
                   'b' => {
                            'b' => 1
                          }
                 }
        };