$passed_tests = 0;
$string =~ /^[\x20-\x7E]+$/ and $passed_tests++; #only printable chars
$string =~ /[^a-zA-Z]/      and $passed_tests++; #>=1 char that isn't a letter

if ($passed_tests == 2) {
   print 'validated';
}
else {
   print 'validation failed';
}