Syntax::Construct - Identify which non-feature constructs are used in the code.
Version 0.19
For some new syntactic constructs, there is the feature pragma. For the rest, there is Syntax::Construct.
use Syntax::Construct qw( // ... /r ); my $x = shift // 'default'; my $y = $x =~ s/de(fault)/$1/r; if ($y =~ /^fault/) { ... }
There are two subroutines (not exported) which you can use to query the lists of constructs programmatically: introduced and removed (see below).
introduced
removed
my @constructs = Syntax::Construct::introduced(); say "$_ was introduced in ", Syntax::Construct::introduced($_) for @constructs;
This module provides a simple way of specifying syntactic constructs that are not implemented via the feature pragma, but are still not compatible with older versions of Perl.
It's the programmer's responsibility to track the constructs and list them (but see Perl::MinimumVersion on how to extract the information from existing code).
Using use Syntax::Construct qw( // ); doesn't really change anything if you're running Perl 5.10+, but it gives much better error messages in older versions:
use Syntax::Construct qw( // );
Unsupported construct //
instead of
Search pattern not terminated
Three groups of people can benefit from the module:
The authors of the module using Syntax::Construct win, as they have all the constructs in one place (i.e. Syntax::Construct's documentation) and they don't waste their time searching through perldeltas and other places.
Users of their modules win as they get meaningful error messages telling them what Perl version they need to upgrade to.
The programmer they hired to workaround the problem wins as they know what constructs to replace in the code to make it run in the ancient version.
Nothing. Using Syntax::Construct with no parameters is an error, giving it an empty list is a no-op (but you can then access the introduced and removed subroutines).
Without arguments, returns a list of all the supported constructs. With an argument, returns the version in which the given construct was introduced.
Same as introduced, but for removed constructs (e.g. auto-deref in 5.24).
"Recursive sort subs" in perl5100delta.
"Defined-or operator" in perl5100delta or "Logical Defined-Or" in perlop.
"Recursive Patterns" under "Regular expressions" in perl5100delta or "(?PARNO) (?-PARNO) (?+PARNO) (?R) (?0)" in perlre.
"Named Capture Buffers" under "Regular expressions" in perl5100delta or "(?<NAME>pattern)" in perlre.
Not mentioned in any Delta. See (?|pattern) in "Extended patterns" in perlre.
"Possessive Quantifiers" under "Regular expressions" in perl5100delta or "Quantifiers" in perlre.
"Backtracking control verbs" under "Regular expressions" in perl5100delta or "Special Backtracking Control Verbs" in perlre.
"\K escape" under "Regular expressions" in perl5100delta or "Look-Around Assertions" in perlre.
"Vertical and horizontal whitespace, and linebreak" under "Regular expressions" in perl5100delta or "Misc" in perlrebackslash.
"Relative backreferences" under "Regular expressions" in perl5100delta or "Capture groups" in perlre.
"Default argument for readline()" in perl5100delta.
"Stacked filetest operators" in perl5100delta.
/p (preserve) modifier and ${^PREMATCH}, ${^MATCH} and ${^POSTMATCH} variables. Not mentioned in any Delta. See "Variables related to regular expressions" in perlvar.
/p
${^PREMATCH}
${^MATCH}
${^POSTMATCH}
"New package NAME VERSION syntax" in perl5120delta
"The ... operator" in perl5120delta or "The Ellipsis Statement" in perlsyn
"each, keys, values are now more flexible" in perl5120delta
"delete local" in perl5120delta
See the ninth bullet in "Other potentially incompatible changes" in perl5120delta.
"\N experimental regex escape" in perl5120delta.
readdir in a while-loop condition populates $_. Not mentioned in any delta, but see readdir in perlfunc.
readdir
$_
"Regular Expressions" in perl5140delta.
"Regular Expressions" in perl5140delta and "Modifiers" in perlre.
"Array and hash container functions accept references" in perl5140delta. See also push, pop, shift, unshift, splice, keys, values, and each in perlfunc.
push
pop
shift
unshift
splice
keys
values
each
See New global variable ${^GLOBAL_PHASE} under "Other Enhancements" in perl5140delta.
"Regular-expressions" in perl5140delta.
See package block syntax under "Syntactical Enhancements" in perl5140delta.
No non-feature constructs were introduced in this version of Perl.
"Computed Labels" in perl5180delta
"subs now take a prototype attribute" in perl5200delta
"rand now uses a consistent random number generator" in perl5200delta
"New slice syntax" in perl5200delta
"Unicode 6.3 now supported" in perl5200delta
See New \p{Unicode} regular expression pattern property in "Core Enhancements" in perl5200delta.
"use locale now works on UTF-8 locales" in perl5200delta
"New double diamond operator" in perldelta
"New b boundaries in regular expressions" in perldelta
"Non Capturing Regular Expression Flag" in perldelta
"Unicode 7.0 with correction is now supported" in perldelta
"New :const subroutine attribute" in perldelta
"fileno now works on directory handles" in perldelta
"Assignment to list repetition" in perldelta
"Floating point parsing has been improved" in perldelta
"Packing infinity or not a number into a character is now fatal" in perldelta
"List slices returning empty lists" in perldelta
"qr foo x now ignores all Unicode pattern white space" in perldelta
E. Choroba, <choroba at cpan.org>
<choroba at cpan.org>
Please report any bugs or feature requests to the GitHub repository, see below.
In development versions of Perl, the removal of constructs is tested against the coming stable version -- e.g., 5.23 forbids all the removed constructs of 5.24. The behaviour of the module in such circumstances might still be, um, unstable.
You can find documentation for this module with the perldoc command.
perldoc Syntax::Construct
You can also look for information at:
GitHub Repository
https://github.com/choroba/syntactic-construct
Feel free to report issues and submit pull requests.
MetaCPAN, Open Source Search Engine for CPAN
https://metacpan.org/pod/Syntax::Construct
AnnoCPAN: Annotated CPAN documentation
http://annocpan.org/dist/Syntax-Construct
CPAN Ratings
http://cpanratings.perl.org/d/Syntax-Construct
Search CPAN
http://search.cpan.org/dist/Syntax-Construct/
Perl::MinimumVersion
Copyright 2013 - 2015 E. Choroba.
This program is free software; you can redistribute it and/or modify it under the terms of the the Artistic License (2.0). You may obtain a copy of the full license at:
http://www.perlfoundation.org/artistic_license_2_0
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This license includes the non-exclusive, worldwide, free-of-charge patent license to make, have made, use, offer to sell, sell, import and otherwise transfer the Package with respect to any patent claims licensable by the Copyright Holder that are necessarily infringed by the Package. If you institute patent litigation (including a cross-claim or counterclaim) against any party alleging that the Package constitutes direct or contributory patent infringement, then this Artistic License to you shall terminate on the date that such litigation is filed.
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To install Syntax::Construct, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Syntax::Construct
CPAN shell
perl -MCPAN -e shell install Syntax::Construct
For more information on module installation, please visit the detailed CPAN module installation guide.