[squid-users] External helper problem

Hello,
I am trying to use my own external helper with squid (currently i am
checking 3.3.2 version). Here is my helper code used for testing(bl.pl
file):

#!/usr/bin/perl
while ($l=<>) {
        print "OK\n";
}

And here is my squid.conf file:

http_port 127.0.0.1:1234
acl dstip1 myip 127.0.0.1
tcp_outgoing_address 127.0.0.1 dstip1

cache deny all
forwarded_for transparent

#user/pass auth
auth_param basic program /usr/local/squid/libexec/ncsa_auth
/usr/local/squid/etc/5.passwd
auth_param basic children 2
auth_param basic realm Squid proxy-caching web server
auth_param basic credentialsttl 2 hours
auth_param basic casesensitive off
acl ncsa_users proxy_auth REQUIRED

#Blacklists
external_acl_type blacklist %DST %LOGIN /usr/local/squid/libexec/bl.pl
acl blacklist_acl external blacklist %DST %LOGIN

# HTTP ACCESS
http_access allow blacklist_acl
http_access allow all

Squid runs fine, helpers are running also and receiving input from
squid. But i cannot connect to the localhost/test123 page (i am
testing at the localhost) - squid seems to process my request forever
without accept/deny. If i remove line with http_access allow
blacklist_acl it works fine - so i am sure this is helper problem.
What am i doing wrong?

Additional question - how to debug such helper problems - is there any
way to get squid log sending request to helper and getting response
from it?

-- 
Regards,
Mateusz Kamiński