# Lesen
open my $fh, '<', $filename or die "$filename: $!\n";
# ...
close $fh;

# Schreiben
open my $wh, '>', $filename     or die "$filename: $!\n";
print $wh "Hello World\n"       or die "print to $filename: $!\n";
close $wh                       or die "close $filename: $!\n";