Learn about exec vs. system first.

[Erich Schubert]

> open(M,"|-") || print "Problem with Domain Forwarding (Fork not \
> possible)" && exit 111;
> $uservariable="$ENV{LOCAL}\@$ARGV[0]";
> exec "/var/qmail/bin/qmail-inject",$uservariable || print "Problem \ 
> with Domain Forwarding (Could not execute qmail-inject)" && exit 111;
> if ($result == 0){
>   while(<STDIN>) { print M $_; }
> }
> close M;

As i told you before, this script will *not* work as supposed.
Read the Documentation about "exec" vs. "system"...

Greetings,
Erich