use vars qw( $log_file );
$log_file = "T:/err.log";

package TeeStderr;

use Fcntl qw(:flock);

sub TIEHANDLE { my $i; bless \$i, shift }

sub PRINT {
    my $r = shift;
    print "STDERR $$ ", @_;

    if ( open my $FH, '>>', $log_file ) {
        flock $FH, LOCK_EX;
        print $FH "" . localtime, "\t", "ErrorLog: ", "", $$, " ", @_;
        close $FH;
    }
}

package main;

$| = 1;
tie *STDERR, "TeeStderr";