open IN, "d1.txt" or die "No such file:$!\n";
open OUT, ">ABC.txt" or die;
while(<IN>)
{
   chomp $_;
$a[$l]=$_;
++$l;
}
my @array=qw(doxorubicin is a potent anti-estrogen drug and tamoxifen);
for($i=0;$i<$l;++$i)
{
foreach $z(@array)
	{
	  if($z=~m/\b\w^$a[$i]$\b/i)
		{
	
		$z=~s/$z/<span style="background-color:yellow;">$z<\/span>/;
		$i++;
	print "@array ";
		
		}
	
	}
	
}

##</code><code>##

(5r)-6-(4-{[2-(3-Iodobenzyl)-3-Oxocyclohex-1-En-1-Yl]Amino}Phenyl)-5-Methyl-4,5-Dihydropyridazin-3(2h)-One

show range error at 2-(