I have found this to be a realy good error log for Perl.

use strict;
use warnings;

# Log Perl Warnings and Errors - Standard
# may have to make the blank file "error.log".
    use CGI::Carp qw(carpout);
    open(LOG, '>>', './error.log')
        or die "Unable to append to at $!\n";
    carpout(*LOG);
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This should log all warnings errors.
Works the best when use strict and use warnings are used.