chop (%key_hash = map { split /\s*[|]\s*/,$_,2 } grep (!/^$/,<KEY_FH>));
  ^                             ^  ^  ^    ^ ^            ^      ^
  |                             |  |  |    | |            |      |
  |                             |  |  |    | |            |      + - File handle
  |                             |  |  |    | |            + - Let only non-empty file lines pass
  |                             |  |  |    | + - Split string into two parts
  |                             |  |  |    + - Default scalar containing a file line
  |                             |  |  + - Zero or more whitespaces
  |                             |  + - Vertical bar as only member in character set
  |                             + - Zero or more whitespaces
  + - Should be 'chomp' to remove the trailing newlines

##</code><code>##

use strict;
use warnings;
use Data::Dumper;

chomp (my %key_hash = map { split /\s*[|]\s*/,$_,2 } grep (!/^$/,<DATA>));

print Dumper \%key_hash;

__DATA__
AAA|B|C|D|E
BBB|G|H|I|J
CCC|1|2|3|4
DDD|6|7|8|9

##</code><code>##

$VAR1 = {
          'CCC' => '1|2|3|4',
          'BBB' => 'G|H|I|J',
          'DDD' => '6|7|8|9',
          'AAA' => 'B|C|D|E'
        };