while ( $line = <$sock> ) {
        push @output, $line;
    }
    print $sock "BYE\n";

##</code><code>##

# In the server script
sub process {
   ...
           print $new_sock <<EOF;
OK
$output
123 End of output
EOF
}

# In the CGI script
sub execute
{
    while ( ($line = <$sock>) !~ /^123/ ) {
        push @output, $line;
    }
    print $sock "BYE\n";
}