A regex that checks values like that is going to be far too complex to maintain. You're better off using a function that checks for valid dates. The timelocal function from Time::Local, converts a list of values (like those returned from localtime) into a epoch seconds value and it dies if passed an invalid date. You can use eval to catch and report on those errors.

#!/usr/bin/perl

use strict;
use warnings;

use Time::Local;

while (<DATA>) {
  chomp;
  my ($y, $m, $d) = split /-/;

  eval { timelocal 0, 0, 0, $d, $m-1, $y-1900 };

  if ($@) {
    print "$_ is not a valid date\n";
  } else {
    print "$_ is a valid date\n";
  }
}

__DATA__
2006-10-30
2006-10-32
2006-02-29
2004-02-29
[download]

It's simple enough to wrap that up into a is_valid_date function.

Enjoy,
Mickey

use Regexp::Assemble;
use Date::Calc;
my $re = Regexp::Assemble->new;
for my $y ( 1900 .. 2100 ) {
  for my $m ( 1 .. 12 ) {
    for my $d ( 1 .. 31 ) {
      if ( Date::Calc::check_date( $y, $m, $d ) ) {
        $re->add( sprintf( "^%4d.%02d\.%02d\$", $y, $m, $d ) );
      }
    }
  }
}

print $re;
[download]

It seems a little counterproductive to call Date::Calc::check_date almost 75,000 times in order to create that regular expression. Unless you're planning to process more than 75,000 records then it would be more efficient to just call Date::Calc::check_date once for each date you want to check.

--
<http://dave.org.uk>

"The first rule of Perl club is you do not talk about Perl club."
-- Chip Salzenberg

Hey, thats more a joke, but Im the only one that does it with a regexp. And I call the script only once and put the resulting regexp into the script. If I need to do it with a regexp.
Boris

boolean DateCalc_check_date(Z_int year, Z_int month, Z_int day)
{
    if ((year >= 1) and
        (month >= 1) and (month <= 12) and
        (day >= 1) and
        (day <= DateCalc_Days_in_Month_[DateCalc_leap_year(year)][mont
+h]))
            return(true);
    return(false);
}
[download]

boolean DateCalc_leap_year(Z_int year)
{
    Z_int yy;

    return( ((year AND 0x03) == 0) and
            ( (((yy = (Z_int) (year / 100)) * 100) != year) or
                ((yy AND 0x03) == 0) ) );
}

const Z_int DateCalc_Days_in_Year_[2][14] =
{
    { 0, 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 },
    { 0, 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 }
};

const Z_int DateCalc_Days_in_Month_[2][13] =
{
    { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
    { 0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
};
[download]

If you install the Date::Calc module correctly, then the C portions will be compiled, installed and linked to the Perl code in Date/Calc.pm. You'll then be able to call it from your Perl code by following the examples in the documentation. The fact that it's written in C won't effect you at all.

Maybe it's worth pointing out that my solution works with a standard Perl installation.

--
<http://dave.org.uk>

"The first rule of Perl club is you do not talk about Perl club."
-- Chip Salzenberg