use strict;
use warnings;

use vars qw( $LOG_FILE_NAME );

BEGIN {
   if (@ARGV && $ARGV[0] =~ /^-?-log(?:=(.*))?$/) {
      *LOGGING = sub () { 1 };
      $LOG_FILE_NAME = $1;
   } else {
      *LOGGING = sub () { 0 };
   }
}

if (LOGGING) {
   if (defined($LOG_FILE_NAME)) {
      open(LOG_FH, '>>', $LOG_FILE_NAME)
      or die("Can't open log file: $!\n");
   } else {
      open(LOG_FH, '>&STDERR')
      or die("Can't dup STDERR: $!\n");
   }
}

print LOG_FH ('Opening log file at '.localtime().".$/") if LOGGING;