my %code = do { my $i = 0; map { $_ => $i++ } split /,/, $tokens };

##</code><code>##

my %code = sub { map { $_[$_] => $_ } 0..$#_ }->( split /,/, $tokens );

##</code><code>##

my $i = 0;
my %code = map { $_ => $i++ } split /,/, $tokens;

##</code><code>##

my @code = split /,/, $tokens;
my %code = map { $code[$_] => $_ } 0..$#code;