Hello pvfki,

When I run your code as written, it works as expected with no errors or warnings. I note that the uninitialized message refers to “line 17” which doesn’t correspond to the code you’ve shown. So I don’t know what the actual problem may be.

A few observations:

• In modern Perl, the preferred style is to use a scalar variable for a file handle: open(my $N, '<', $filename);
• You should check each open and close for possible failure. The simplest way to do this is by adding use autodie; to the head of your script.
• Prefer the 3-argument form of open for writing as well as reading: open(my $FILE, '>', $outfile);
• Since you explictly close FILE;, you should also close N;.

Extending the script to process multiple lines just requires a loop:

use warnings 'all';
use strict;
use autodie;

my $filename = 'numbers.txt';
my $outfile  = 'sum.txt';

open(my $in,  '<', $filename);
open(my $out, '>', $outfile);

while (my $numbers = <$in>)
{
    chomp $numbers;
    my $sum = eval $numbers;
    print $out $sum, "\n";
}

close $out;
close $in;
[download]

Hope that helps,

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