open my $ifh, '<', $filename or die "$filename: $!";
chomp( my @array = <$ifh> );
close $ifh;

# modify @array here

open my $ofh, '>', $filename or die "$filename: $!";
print $ofh $_,"\n" for @array;
close $ofh;

##</code><code>##

use File::Replace;
 
my $repl = File::Replace->new($filename);
my $infh = $repl->in_fh;
while (my $line = <$infh>) {
    chomp($line);
    # modify $line here
    print {$repl->out_fh} $line, "\n";
}
$repl->finish;