Thanks Larsen, I did try to write my own constraint and though it does not give me any error, it does not perform the validation. Here is my code-

my $profile = {
            required => ['holidayfrom','holidayto'],
            optional => ['usercomments'],
            filters        => ['trim'],
            constraints => {
                hoidayto => {
                    params => [ 'holidayfrom', 'holidayto' ],
                    constraint => sub {
                                my $from = shift;
                                my $to   = shift;
                        my ($d1,$m1,$y1) = split("/",$from);
                        my ($d2,$m2,$y2) = split("/",$to);
                        my $Dd = Delta_Days(
                                    $y1, $m1, $d1,
                                    $y2, $m2, $d2
                                );
                        if($Dd < 0){return 1;}
                        return 0;
                    }
                }
            },
            msgs=>{
                any_errors => 'err__',
                prefix=>'err_',
            },
        };
[download]

I am sure I am making some basic mistake. I am fairly new to Perl.