#!/usr/bin/perl -lw
use strict ;

my $d = "2005-12-" ;
if ( $d =~ /\d{4}-\d{1,3}(?!-)/ ) {
  print "yep" ;
}
##</code><code>##

\d{4}-\d{1,3}(?!-)$
\d{4}-\d{2}(?!-)