less5.18(3pm) [mojave man page]

less(3pm)						 Perl Programmers Reference Guide						 less(3pm)

NAME

       less - perl pragma to request less of something

SYNOPSIS

	   use less 'CPU';

DESCRIPTION

       This is a user-pragma. If you're very lucky some code you're using will know that you asked for less CPU usage or ram or fat or... we just
       can't know. Consult your documentation on everything you're currently using.

       For general suggestions, try requesting "CPU" or "memory".

	   use less 'memory';
	   use less 'CPU';
	   use less 'fat';

       If you ask for nothing in particular, you'll be asking for "less 'please'".

	   use less 'please';

FOR MODULE AUTHORS

       less has been in the core as a "joke" module for ages now and it hasn't had any real way to communicating any information to anything.
       Thanks to Nicholas Clark we have user pragmas (see perlpragma) and now "less" can do something.

       You can probably expect your users to be able to guess that they can request less CPU or memory or just "less" overall.

       If the user didn't specify anything, it's interpreted as having used the "please" tag. It's up to you to make this useful.

	 # equivalent
	 use less;
	 use less 'please';

   "BOOLEAN = less->of( FEATURE )"
       The class method "less->of( NAME )" returns a boolean to tell you whether your user requested less of something.

	 if ( less->of( 'CPU' ) ) {
	     ...
	 }
	 elsif ( less->of( 'memory' ) ) {

	 }

   "FEATURES = less->of()"
       If you don't ask for any feature, you get the list of features that the user requested you to be nice to. This has the nice side effect
       that if you don't respect anything in particular then you can just ask for it and use it like a boolean.

	 if ( less->of ) {
	     ...
	 }
	 else {
	     ...
	 }

CAVEATS

       This probably does nothing.
       This works only on 5.10+
	   At least it's backwards compatible in not doing much.

perl v5.18.2							    2013-11-04								 less(3pm)

feature(3pm)						 Perl Programmers Reference Guide					      feature(3pm)

NAME

       feature - Perl pragma to enable new features

SYNOPSIS

	   use feature qw(switch say);
	   given ($foo) {
	       when(1) 	 { say "$foo == 1" }
	       when ([2,3])	 { say "$foo == 2 || $foo == 3" }
	       when (/^a[bc]d$/) { say "$foo eq 'abd' || $foo eq 'acd'" }
	       when ($_ > 100)	 { say "$foo > 100" }
	       default		 { say "None of the above" }
	   }

	   use feature ':5.10'; # loads all features available in perl 5.10

DESCRIPTION

       It is usually impossible to add new syntax to Perl without breaking some existing programs. This pragma provides a way to minimize that
       risk. New syntactic constructs, or new semantic meanings to older constructs, can be enabled by "use feature 'foo'", and will be parsed
       only when the appropriate feature pragma is in scope.

   Lexical effect
       Like other pragmas ("use strict", for example), features have a lexical effect. "use feature qw(foo)" will only make the feature "foo"
       available from that point to the end of the enclosing block.

	   {
	       use feature 'say';
	       say "say is available here";
	   }
	   print "But not here.
";

   "no feature"
       Features can also be turned off by using "no feature "foo"". This too has lexical effect.

	   use feature 'say';
	   say "say is available here";
	   {
	       no feature 'say';
	       print "But not here.
";
	   }
	   say "Yet it is here.";

       "no feature" with no features specified will turn off all features.

   The 'switch' feature
       "use feature 'switch'" tells the compiler to enable the Perl 6 given/when construct.

       See "Switch statements" in perlsyn for details.

   The 'say' feature
       "use feature 'say'" tells the compiler to enable the Perl 6 "say" function.

       See "say" in perlfunc for details.

   the 'state' feature
       "use feature 'state'" tells the compiler to enable "state" variables.

       See "Persistent Private Variables" in perlsub for details.

   the 'unicode_strings' feature
       "use feature 'unicode_strings'" tells the compiler to treat all strings outside of "use locale" and "use bytes" as Unicode. It is available
       starting with Perl 5.11.3.

       See "The "Unicode Bug"" in perlunicode for details.

FEATURE BUNDLES

       It's possible to load a whole slew of features in one go, using a feature bundle. The name of a feature bundle is prefixed with a colon, to
       distinguish it from an actual feature. At present, the only feature bundle is "use feature ":5.10"" which is equivalent to "use feature
       qw(switch say state)".

       Specifying sub-versions such as the 0 in 5.10.0 in feature bundles has no effect: feature bundles are guaranteed to be the same for all
       sub-versions.

IMPLICIT LOADING

       There are two ways to load the "feature" pragma implicitly :

       o   By using the "-E" switch on the command-line instead of "-e". It enables all available features in the main compilation unit (that is,
	   the one-liner.)

       o   By requiring explicitly a minimal Perl version number for your program, with the "use VERSION" construct, and when the version is
	   higher than or equal to 5.10.0. That is,

	       use 5.10.0;

	   will do an implicit

	       use feature ':5.10';

	   and so on. Note how the trailing sub-version is automatically stripped from the version.

	   But to avoid portability warnings (see "use" in perlfunc), you may prefer:

	       use 5.010;

	   with the same effect.

perl v5.12.5							    2012-11-03							      feature(3pm)