Ubuntu Manpage: Perl::Critic::Policy::Community::DeprecatedFeatures

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.