use strict;
use warnings;
use Tie::File;

my $file = "inputfile";
 
my @array;

tie @array , 'Tie::File', $file ;

my $start = '<default>';
my $end   = '</default>';
my $val   = 'enabled';
my $replace = $start.$val.$end;
print "replace $replace \n";

for (my $i = 0 ; $i <= $#array ; $i++)
{
    #below if block is tried for multiple line pattern but not working

    # if ($array[$i] =~ /^<default>/../<^\/default>/)

	if($array[$i] =~ /^<default>/) #this is working
	{
		
		$array[$i] =~ s/^<default>.*<\/default>/$replace/g;
		

	}

}
untie @array;