Re: [Boston.pm] catenation of undef with string, 2 cases

On 11/09/2016 03:24 PM, Mike Small wrote:
> Uri Guttman <uri-X/[email protected]> writes:
>
>> On 11/09/2016 02:04 PM, Bill Ricker wrote:
>>> I think Uri and Ricky have it nailed.
>>>
>>> You can
>>> wrap with do{ no warnings; ...  }  or
>>> protect the concatenation with  42 . ($b//q()); or equivalent ?: or or
>>> use $b .= 42 ; if order doesn't matter (it usually does, though)
>>> or initialized $b to '' instead of undef, knowing it will be
>>> concatenated (but in that case be sure it's tested for Truth not
>>> Definedness)
>>>
>>>
>> just to add on, i use .= so often. i like to build up strings and then
>> return the whole string. i never initialize them to '' as i know .=
>> works without warning. this is true for scalars and data structures as
>> i said before. any lvalue undef can be used in this way.
>>
>> uri
>>
> Thanks everyone. Especially thanks for relating it to +=. I have trouble
> remembering the handy special cases but when it's somewhat systematic
> that helps.
>
another systemic and related thing in perl is autovivification. i have 
seen newbies always check for undef and then assigning a hash/array ref 
before adding elements to the hash/array. this is how some other langs 
require things to be done. perl has always had neat shortcuts like 
autoviv and no undef warnings on +=, .= and ++ because those are very 
popular operations and having perl do some init behind the scenes for 
you is way cool.

uri