Looks like your code should read:

chomp($value = <STDIN>);
if($value =~ /(0[1-9]|[12][0-9]|3[01])[- /.](0[1-9]|1[012])[- /.] \d\d
+\d\d)/) {
    print "date";
}else{
    print $value;
    print "not a date";
}
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I notice there's a literal space between [- /.] and \d\d\d\d, which may not be what you intended. That's if I've correctly deciphered your very poorly formatted post.