sub display
{
    my ($self)  = @_;
    my  $output = '';

    if ($self)
    {
        $output  = sprintf "Name:       %s\n", $self->{NAME};
        $output .= sprintf "Age:        %d\n", $self->{AGE};
        $output .= sprintf "Regd no:    %s\n", $self->{REGD_NO};
        $output .= sprintf "Phone num:  %s\n", $self->{PHONE_NUM};
        $output .= sprintf "Mark:       %d\n", $self->{MARK};
        $output .= sprintf "Pass year:  %d\n", $self->{PASS_YEAR};
    }

    return $output;
}

##</code><code>##

my $outfile = 'temp.txt';
open(my $fh, '>', $outfile) or die "Cannot open file '$outfile' for writing: $!";
print $fh find_student('x3')->display();
close($fh)                  or die "Cannot close file '$outfile': $!";