#!/usr/bin/perl
print "effective: $>, real: $<\n";
$> = 111;
open(O,">foo") or die "Can't write foo: $!\n";
close O or die "Can't close O: $!\n";
$> = 0;
open(O,">bar") or die "Can't write bar: $!\n";
close O or die "Can't close O: $!\n";
$> = 111 ;
# this must fail.
open(O,">bar") or warn "Can't write bar: $!\n";
# change real uid
$< = 111; # oops, forgot to set $> to 0
print "effective: $>, real: $<\n";
$< = 0;   # no effect
print "effective: $>, real: $<\n";