Question

This is in continuation with this ->Read and Write to a file in perl question.

The following code worked perfectly fine for reading and writing to the same file:

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

my $filename = "out.txt";
my @array;
tie @array, 'Tie::File', $filename
    or die "can't tie file \"$filename\": $!";

for my $line (@array) {

    $line = "<$line>";
}
untie @array;

But when I did the following the changes were not reflected in the file :

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

my $filename = "out.txt";
my @array;
tie @array, 'Tie::File', $filename
    or die "can't tie file \"$filename\": $!";

my $len = @array;
for ($i = 0; $i < $len ; $i++) {

    $line = $array[$i];
    $line = "<$line>";     
}
untie @array;

Can someone help me with this problem ?
Yes I know I can use the for loop above, knowing this may help me solve some other problems too.
Thank you.

Answer 1

In the first snippet, you’re modifying the elements of @array (via the alias $line).

In the second, you’re not modifying any elements of @array. Change

$line = $array[$i];
$line = "<$line>";

to

$line = $array[$i];
$line = "<$line>";
$array[$i] = $line;

or simply

$array[$i] = "<$array[$i]>";

Note that using Tie::File is an awful way to do what you are doing.