Up to Perl 5.8.6, it was perfectly legal to open a pipe like this and not worry about $ENV{'PATH'} (notice the -T flag):

#!/usr/bin/perl -wT

use strict;

$SIG{'PIPE'} = 'IGNORE';
$| = 1;

my $pid = open CONSUMER, '|-';
if (!defined $pid) {
    die "cannot fork: $!";
}
if (!$pid) {
    open STDOUT, '/dev/null';
    my $msg = <STDIN>;
    exit(0);
}
print CONSUMER "hi there\n" or die "cannot write to pipe: $!";
close CONSUMER
    or die $! ? "error closing pipe: $!" : "child exit status: $?";
print "done, satisfied\n";
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However, Perl 5.8.7, 5.8.8 and 5.9.3 won't allow that any longer, insisting that $ENV{PATH} should be set to something secure before executing the open.

I wonder why that is. The environment should be checked before exec and the like, but what is wrong with a simple fork eludes me. Especially since the other piping direction '-|' appears to trigger no such paranoia.

Am I overlooking something or could this be a Perl bug? I'd like to not interfere with global variables like %ENV unless I must.

Update:

The error message I am getting is: Insecure $ENV{PATH} while running with -T switch at /home/martin/example line 8.

And indeed, inserting a line $ENV{'PATH'} = '/bin'; just before the open makes Perl happy if not me.