while ($_ = substr($foo,$i++,1)){
	if (++$_**2 == 0) {
		print "$foo Contains Alpha Characters\n";
		last;
	} 
}

##</code><code>##

my $i = 0;
while (local $_ = substr($foo,$i++,1)){
	if (++$_ == 0) {
		print "$foo Contains Alpha Characters\n";
		last;
	} 
}

##</code><code>##

while (++substr($foo,$i++,1) != 0){}