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
