my $string= '62880147894644072';

substr( $string, 0, -4 ) =~ tr//*/c;

print $string, $/;
[download]

Note that I substituted my own credit card number for yours in my test code. ;)

Update: ++ to Sidhekin for out golfing me while I was previewing. ( I like this solution because I find it clear, not because it involves fewer keystrokes. :)

I like this solution a lot as well, both for clarity and because it maintains the flexibility of the original code demonstrated in the update to my original post. Very elegant.

---
It's all fine and dandy until someone has to look at the code.

$ perl -le'
my $string = q/5424123412345678/;
$string =~ s/.(?=.{4})/*/g;                   
print $string;'
************5678

Update:

$ perl -le'
my $string = q/5424123412345678/;
$string =~ s/(?<=.{4}).(?=.{4})/*/g;
print $string;'
5424********5678
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29, counting the semicolon. :-)

my $string = '5424123412345678';
substr($string,0,-4)=~y//*/c;
print $string;
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Here's one to be different:

echo "1234567890123456" | 
perl -lne 'print"\*"x(length()-4),scalar reverse unpack "A4",reverse'
[download]

gratias vobis ago valeteque
-v.

Maybe a regex:

$string =~ s/^\d{12}/'*' x 12/e;           # ************5678
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If the OP wanted to hardcode the length, he could have done

substr($string,0,-4,'*'x12);
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Much clearer.

my $string = '5424123412345678';
substr$_,0,-4,'*'x(length()-4)for$string;  # 41
print $string;
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my $string = '5424123412345678';
s/(?!.{0,4}$)./*/g for$string;  # 30
print $string;
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Update: More readable than the previous:

my $string = '5424123412345678';
$string=~s/(?!.{0,4}$)./*/g;  # 28
print $string;
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Here's 25: $string=~s/.(?=....)/*/g;

---

Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart

jwkrahn beat you to 25 with $string=~s/.(?=.{4})/*/g;

More clean:

$string = '*' x 12 . substr($string,-4);   # ************5678
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 printf "%-12.12s****\n", '5424123412345678';;
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Update: Hmm. Misread your code. I thought you were obscuring the last 4 digits.

This will do the first twelve for a score of ...um...either 0 or -30-somthing :)

[0] Perl> printf "************%4.4s\n", '5424123412345678';;
************5424
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Still not right. It should be printing the *last* four (************5678).

Ah! Then

printf "************%s\n", substr('5424123412345678', -4);;
************5678
[download]

---

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal?

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

More fuzzy (the result)

substr($string,rand length $string,1,"*") foreach 1..12;   # 5****23**
+*34**7*
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That's bad for readability (harder for the user to figure out which one of his cards was used), and it's bad security (since the number could be obtained over time or if multiple retailers did this). And of course, there's are times when two, one and even no digits are hidden.

I know one bank that use it... but I agree with you...

Actually a couple issues with this, 1) not guaranteed to use any asterisks (usually will), 2) since they are different each time with enough receipts you could get the whole number.

                - Ant
                - Some of my best work - (1 2 3)