#!perl -w
use strict;
use warnings;
use subs qw(open);
use Errno qw(EPIPE);

sub open {
    $! = EPIPE;
    warn "open faked";
    return 0;
}

Test::subs();
exit(0);

package Test;

sub subs {
    my $string = "hello world";
    local *STDIN;
    open(STDIN, '<', \$string) or die "open failed: $!";
    binmode STDIN;

    while(<>) {
        print;
    }
}

1

##</code><code>##

local *IO::File::open = sub {.....}

##</code><code>##

#!perl -w
use warnings;
use Errno qw(EPIPE);
use lib qw(.);
eval "use Test;";

BEGIN {
*{main::open} = sub {
    $! = EPIPE;
    warn "open faked";
    return 0;
};
}

Test::subs();
exit(0);

##</code><code>##

package Test;

sub subs {
    my $string = "hello world";
    local *STDIN;
    open(STDIN, '<', \$string) or die "open failed: $!";
    binmode STDIN;

    while(<>) {
        print;
    }
}

1