John said:
Part of code.
If hash does not exist make it null.
Is this the correct syntax?
my %data; my $hash=\%data;
.......
my $error=$hash->{error} or '';
It is correct, but more than a little weird: There is no reason to
declare a hash and assign a reference to that to a scalar variable to
get a hash reference. Provided that a hash reference is what it
actually desired,
my $hash = {};
or just using $hash as hash references in an lvalue context would be
sufficient, eg
my $hash;
$hash->{key} = 'value';
Also, for a sufficiently recent version of Perl,
my $error = $hash->{error} // '';
might be a better choice because it only uses the empty string in
place of the value stored in the hash when this value happened to be
undefined, as opposed to 'something evaluating to false', ie, an empty
string or a numerical zero.
Lastly, this smells a lot like trying to obfuscate one's way around
the "It is undef! Panic in the streets!!" warning somebody has chosen
to code into Perl for some weird reason. A good solution for the
'computer prints nonsense when doing X' problem is 'not doing X', in
this case, not running with warnings enabled.