I suggest Data::Password which will give you a true/false on whether a password is good or not. The defaults are good for general purposes, but all of the types of validation are configurable.

As for your direct question, no your set won't work. There are two steps you need to take, if you choose not to use a module (though I highly recommend module use). First, make sure there are no *invalid* chars in the password, then make sure you have minimums of your various requirements. In your case:

$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';
}
[download]

A simple search on CPAN returns dozens of possibilities.

I can't comment on or recommend any particular module, as I've not used any of them myself. However, I would recommend using a module rather than trying to pre-cook your own regular expression - why re-invent the wheel?