I'll do this in two steps. First I'll check that the date is indeed eight digits, then I'll check if it refers to a valid date with the Date::Manip module (so this will fail with historical dates using the Julian calendar). 

perl -we 'use Date::Manip; sub valid_yyyymmdd { $_[0] =~ /^(\d{8})$/ a
+nd ParseDate($1) and 1; } valid_yyyymmdd($_) and print "$_\n" for qw"
+20060630 20060631 20060730 20060731 20060732 2006.07.30 06.07.31";'

[download]
Output: 
20060630
20060730
20060731

[download]

In reply to Re: checking for valid date by ambrus
in thread checking for valid date by alandev

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