Defined-or '//'

You shall be careful with Perl's idea about booleans. Real bools to not exist, but every value also has a true or false attached to it.

For completeness, here the table

undef      false     undefined / uninitialized
""         false     empty string
0          false     zero, nothing
@x         false     when empty
"0"        false(!)  the string zero
0.0        false     float 0, dangerous wrt rounding errors

A common sloppiness is a sleeping bug:

$filename or die "No filename given.\n";

This usually works, but produces an error when the filename is "0". So, the correct code would be

defined $filename or die "No filename given.\n";

More difficult is this case, with a common way to express fallback values:

my $pay = $action_price || $normal_price || die "No price";

Is a price of '0' ever acceptable? It will not be picked-up. So, you may need to write:

my $pay = defined $action_price ? $action_price : defined $normal_price ? $normal_price : die;

Perl 5.10 introduced "//", the defined-or. In this case, only an undefined value is considered false:

my $pay = $action_price // $normal_price // die "No price";

Patches

• patch Mail-Message
• patch Mail-Box
• patch Mail-Transport
• patch Mail-Box-IMAP4

Exists

Meanwhile, 4 places where fixed where boolean parameters were not correctly processed. The following accepts only non-undef versions of false as boolean:

my $take = defined $args{take} ? $args{take} : 1;

Corrected into:

my $take = exists $args{take} ? $args{take} : 1;