# forks then changes working directory and executes a command
sub chdir_and_system {
	my ( $dir, @exec_args ) = @_;
	my $pid = fork;
	die "couldn't fork: $!" unless defined $pid;
	unless ($pid) {              # this is the child
		chdir($dir);

	   # open STDOUT, ">/dev/null";    # silence subprocess output
	   # open STDERR, ">/dev/null"; # silence subprocess stderr
		system(@exec_args) == 0 
			or die "system @exec_args failed";
	}
	wait;
	die "child error $?" if ($?);
}