The 555 area code is a well-known area code that appears only in Hollywood movies and other fiction stuff. There is even a web page about that: http://home.earthlink.net/~mthyen/

So, if you want to "sanitize" a piece of code containing phone numbers (for privacy reasons and to fight spam... er telemarketing), you replace these by phone numbers from the 555-area.

Yet, maybe Sevrin could have said 555-1234-5678 or 555-2002-0408 :-)

update

I have forgotten the following example. In Mac Perl, Power and Ease (published by Prime Time Freeware http://www.ptf.com/), both authors (Vicki Brown and Chris Nandor) give their phone numbers:

$phone{"Vicki"} = "555-1234";
$phone{"Chris"} = "555-4321"; 

Another update. Sevrin, may be you could look at some of the modules you get in http://search.cpan.org/search?mode=module&query=phone