The module expects the key to be in bytes, not in hexadecimal nibbles:

use strict;
use Crypt::ECB qw(encrypt decrypt encrypt_hex decrypt_hex);

my $ascii_key = "0123456789abcdef";
my $key= "\x01\x23\x45\x67\x89\xab\xcd\xef";

my $plain_text = "Now is the time for all ";
my $expected= '3fa40e8a984d48156a271787ab8883f9893d51ec4b563b53';

my $result= encrypt_hex($key,"DES_PP",$plain_text,0);

if( $result eq $expected ) {
    print "Yay\n";
} else {
    print "Got     : $result\n";
    print "Expected: $expected\n";
};
[download]