BEGIN {
  require 5.004;
  use CGI::Carp qw(fatalsToBrowser carpout);
  my $logfile = 'path/to/logfile';
  open LOG, ">>$logfile" or
    die "Couldn't append to $logfile: $!\n";
  carpout(\*LOG);
};

##</code><code>##

warn "Logging...\n";

##</code><code>##

[Thu Apr  7 05:39:57 2005] testcgi: Logging...