my $inp = "abc.xml";
my $out = "new_abc.xml"; 
open( INP, $inp ) or die "$inp: $!" );
open( OUT, $out ) or die "$out: $!" );

my @array = <INP>;  

my $xml1 = qq|<sample>
 		<date>$date</date>
    	<server>cardev.ebookers</server>
    	<process_Id>$dirn</process_Id>
		<ref_key>$r</ref_key>
		</sample>
		</test>|;

$array[$#array] = $xml1; # replace last line

print OUT join "", @array;