Challenge 1: Write Then Read — Possible Solution
====================================================================

use strict;
use warnings;
use feature 'say';

open(my $out, '>', 'output.txt') or die "Can't open: $!";
print $out "First line\n";
print $out "Second line\n";
print $out "Third line\n";
close($out);

open(my $in, '<', 'output.txt') or die "Can't open: $!";
while (my $line = <$in>) {
    chomp($line);
    say $line;
}
close($in);

Output:
First line
Second line
Third line

WHY THIS WORKS AS AN ANSWER
------------------------------
open(my $out, '>', 'output.txt') or die "..."; reuses the chapter's
own 3-argument open with '>' mode and the required or die error
check, exactly as the chapter's own writing example shows.

print $out "First line\n"; (and the two lines after it) reuse the
chapter's own print $fh "text" syntax precisely — no comma between
$out and the string, per this chapter's own warn-box explaining that
adding one would break the write entirely. Each string includes its
own \n, since print never adds one automatically (Course 1, Chapter
1).

close($out); is called before reopening the same file for reading —
necessary because the write needs to be fully flushed to disk before
a separate read of the same file can reliably see it.

The second open/while/close block reuses the chapter's own
while (my $line = <$fh>) idiom and chomp call exactly, this time with
'<' mode — reading back the three lines just written, stripping each
one's trailing newline before printing it with say, confirming the
write-then-read round trip produced the expected three lines.