my $filename = 'yourfilename.txt';
open FILE, "$filename" || die "cant open file for read";

@data = <FILE>;

close FILE;

for my $line (0..$#data) {

	# execute process method -- do your operation stuffs here.
	
	&process($data[$line]);

	# if you want to delete, make the line with null value;

	$data[$line] = "";

}



$entirefile = join "\n", @data;

open OUT, "outfile.txt" || die "cant open file for write";

print OUT $entirefile;

close OUT;