open(my $fh, '>', 'my_file.txt');

##</code><code>##

or die "...";

##</code><code>##

edit_file('my_file.txt');

##</code><code>##

open(my $fh, '<', $myfile) or die "Unable to open file\n";

while (<$fh>)
{
    chomp;             # <-- here and
    unless (/^[a-z]/)  # <-- here
    {
        ...