struct hek {
    U32         hek_hash;       /* hash of key */
    I32         hek_len;        /* length of hash key */
    char        hek_key[1];     /* variable-length hash key */
    /* the hash-key is \0-terminated */
    /* after the \0 there is a byte for flags, such as whether the key
       is UTF-8 */
};

typedef struct hek HEK;

##</code><code>##

use warnings;
use strict;
my %x = qw/abcd efgh ijkl mnop/;
for (%x) {
   substr $_, 0, 2, "";
   print("$_\n");
}

##</code><code>##

kl
op
cd
gh