use subs 'open';
sub open
{
    print "opening file: @_\n";
    CORE::open(@_);
}

##</code><code>##

    CORE::open($_[0], $_[1]);

##</code><code>##

use subs 'open';

$file = $ARGV[0];
$method = $ARGV[1] eq 'bad' ? 0 : 1;

sub open
{
    my $count = scalar @_;
    print "opening file: @_ ($count)\n";  # Prints "opening file: TEST [filename] (2)" for either method

    my $return;
    if ($method == 0)
    {
	$return = CORE::open(@_);  # doesn't work
    }
    else
    {
	$return = CORE::open($_[0], $_[1]);  # works
    }

    return $return;
}

if ($result = open (TEST, $file))
{
    my $lineCount;
    for my $line (<TEST>)
    {
	last if $lineCount++ > 5;
	print "$line\n";
    }
    close TEST;
}
else
{
    print "couldn't open test.pl\n";
    print "error info: $!\n" if $!;
    print "more error info: $^E\n" if $^E;
}