Ubuntu Manpage: Perl::Critic::Policy::Community::DeprecatedFeatures - Avoid features that have been deprecated or removed

Provided by: libperl-critic-community-perl_1.0.3-1_all

NAME

       Perl::Critic::Policy::Community::DeprecatedFeatures - Avoid features that have been deprecated or removed
       from Perl

DESCRIPTION

       While Perl::Critic::Policy::Community::StrictWarnings will expose usage of deprecated or removed features
       when a modern perl is used, this policy will detect such features in use regardless of perl version, to
       assist in keeping your code modern and forward-compatible.

FEATURES

:=
Because the whitespace between an attribute list and assignment operator is not significant, it was
possible to specify assignment to a variable with an empty attribute list with a construction like "my
$foo := 'bar'". This is deprecated in perl v5.12.0 to allow the possibility of a future ":=" operator.
Avoid the issue by either putting whitespace between the ":" and "=" characters or simply omitting the
empty attribute list.

$[
The magic "$[" in perlvar variable was used in very old perls to determine the index of the first element
of arrays or the first character in substrings, and also allow modifying this value. It was discouraged
from the start of Perl 5, its functionality changed in v5.10.0, deprecated in v5.12.0, re-implemented as
arybase.pm in v5.16.0, and it is essentially a synonym for 0 under "use v5.16" or "no feature
"array_base"". While it is probably a bad idea in general, the modules Array::Base and String::Base can
now be used to replace this functionality.

/\C/
The "\C" regular expression character class would match a single byte of the internal representation of
the string, which was dangerous because it violated the logical character abstraction of Perl strings,
and substitutions using it could result in malformed UTF-8 sequences. It was deprecated in perl v5.20.0
and removed in perl v5.24.0. Instead, explicitly encode the string to UTF-8 using Encode to examine its
UTF-8-encoded byte representation.

?PATTERN?
The "?PATTERN?" regex match syntax is deprecated in perl v5.14.0 and removed in perl v5.22.0. Use
"m?PATTERN?" instead.

autoderef
An experimental feature was introduced in perl v5.14.0 to allow calling various builtin functions (which
operate on arrays or hashes) on a reference, which would automatically dereference the operand. This led
to ambiguity when passed objects that overload both array and hash dereferencing, and so was removed in
perl v5.24.0. Instead, explicitly dereference the reference when calling these functions. The functions
affected are "each", "keys", "pop", "push", "shift", "splice", "unshift", and "values".

Bare here-doc
Using " << " to initiate a here-doc would create it with an empty terminator, similar to " <<'' ", so the
here-doc would terminate on the next empty line. Omitting the quoted empty string has been deprecated
since perl 5, and is a fatal error in perl v5.28.0.

chdir('')
Passing an empty string or "undef" to "chdir()" would change to the home directory, but this usage is
deprecated in perl v5.8.0 and throws an error in perl v5.24.0. Instead, call "chdir()" with no arguments
for this behavior.

defined on array/hash
Using the function "defined()" on an array or hash probably does not do what you expected, and is
deprecated in perl v5.6.2 and throws a fatal error in perl v5.22.0. To check if an array or hash is non-
empty, test if it has elements.

if (@foo) { ... }
if (keys %bar) { ... }

do SUBROUTINE(LIST)
This form of "do" to call a subroutine has been deprecated since perl 5, and is removed in perl v5.20.0.

NBSP in \N{...}
Use of the "no-break space" character in character names is deprecated in perl v5.22.0 and an error in
perl v5.26.0.

POSIX character functions
Several character matching functions in POSIX.pm are deprecated in perl v5.20.0. See the POSIX
documentation for more details. Most uses of these functions can be replaced with appropriate regex
matches.

isalnum, isalpha, iscntrl, isdigit, isgraph, islower, isprint, ispunct, isspace, issuper, isxdigit

POSIX::tmpnam()
The "tmpnam()" function from POSIX.pm is deprecated in perl v5.22.0 and removed in perl v5.26.0. Use
File::Temp instead.

qw(...) as parentheses
Literal parentheses are required for certain statements such as a "for my $foo (...) { ... }" construct.
Using a "qw(...)" list literal without surrounding parentheses in this syntax is deprecated in perl
v5.14.0 and a syntax error in perl v5.18.0. Wrap the literal in parentheses: "for my $foo (qw(...)) { ...
}".

require ::Foo::Bar
A bareword "require" (or "use") starting with a double colon would inadvertently translate to a path
starting with "/". Starting in perl v5.26.0, this is a fatal error.

UNIVERSAL->import()
The method "UNIVERSAL->import()" and similarly passing import arguments to "use UNIVERSAL" is deprecated
in perl v5.12.0 and throws a fatal error in perl v5.22.0. Calling "use UNIVERSAL" with no arguments is
not an error, but serves no purpose.

AFFILIATION

       This policy is part of Perl::Critic::Community.

CONFIGURATION

       This policy is not configurable except for the standard options.

CAVEATS

       This policy is incomplete, as many deprecations are difficult to test for statically. It is recommended
       to use perlbrew or perl-build to test your code under newer versions of Perl, with "warnings" enabled.

AUTHOR

       Dan Book, "dbook@cpan.org"

COPYRIGHT AND LICENSE

       Copyright 2015, Dan Book.

       This library is free software; you may redistribute it and/or modify it under the terms of the Artistic
       License version 2.0.