AW: Regular expression for years after a given one

Jose Alves de Castro wrote:
> Yesterday, a friend of mine was toying around with some Perl 
> code, when he got to a function which would only accept a 
> regular expression. He
> said:
> 
> "How can I say that I want every single year after the one I 
> have? It's impossible..."
> 
> To which I replied:
> 
> "Nothing is impossible! Especially in Perl! ;-) " (ok, maybe 
> these weren't my words at the time, but they seem cool now, 
> right? :-) )
> 
> So after a couple of minutes, this is what I came up with:
> 
> 
> $year = 2004; # I'm stating it directly to improve clarity
> 
> $year =~/(\d)(\d)(\d)(\d)/;
> 
> ($c,$d,$e,$f) = ($4+1,$3+1,$2+1,$1+1);
> 
> $regex =
> qr/^\d*(?:${1}${2}${3}[$c-9]|${1}$2[$d-9]\d|$1[$e-9]\d{2}|[$f-9]\d{3})$/;

Another approach:

use re 'eval';
my $re = qr/(\d{4})(??{ $1>$year?'':'x{1000}' })$/;

Assuming, of course, that $_ never contains a smaller year
number followed by thousand 'x'es. :-)

-Christian