You need to fork a child process to run the background job, so the parent can send the redirection and terminate normally. Also, you'll need to close (or redirect to a file) STDOUT and STDERR in the child before the exec(), so the webserver will not wait for the pipes to the child (duplicated by the fork) to get closed.

Update: something like this:

my $pid = fork();  die "Couldn't fork: $!" unless defined $pid;

if ($pid) {
    # parent
    print "Location: $outpage_url\n\n";
    
} else { # $pid == 0
    # child
    open STDOUT, ">>", "/path/to/some/logfile" or warn "Couldn't redir
+ect STDOUT: $!";
    open STDERR, ">>", "/path/to/some/logfile" or warn "Couldn't redir
+ect STDERR: $!";

    exec "$bin/somescript.pl";
    exit; # just in case the exec failed
}
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