# The array @tag contains around 40000 records
# Input_file.dat contains 30000 lines

open(FH1,"+>Result_file.txt") or die "Cannot create file $!\n";
	foreach my $fkey(@tag) {
		open(FH,"<Input_file.dat") or die "Cannot read $!\n";
                	while(<FH>) {
                 		if($_ =~ m/$fkey/g) {
                                	print FH1 "$_\n";
                 
                        	}
                	}
                close(FH);
        }
close(FH1);