NAME

       B::Lint - Perl lint

SYNOPSIS

       perl -MO=Lint[,OPTIONS] foo.pl

DESCRIPTION

       The B::Lint module is equivalent to an extended version of the -w option of perl. It is
       named after the program lint which carries out a similar process for C programs.

OPTIONS AND LINT CHECKS

       Option words are separated by commas (not whitespace) and follow the usual conventions of
       compiler backend options. Following any options (indicated by a leading -) come lint check
       arguments. Each such argument (apart from the special all and none options) is a word
       representing one possible lint check (turning on that check) or is no-foo (turning off
       that check). Before processing the check arguments, a standard list of checks is turned
       on. Later options override earlier ones. Available options are:

       magic-diamond
               Produces a warning whenever the magic "<>" readline is used. Internally it uses
               perl's two-argument open which itself treats filenames with special characters
               specially. This could allow interestingly named files to have unexpected effects
               when reading.

                 % touch 'rm *|'
                 % perl -pe 1

               The above creates a file named "rm *|". When perl opens it with "<>" it actually
               executes the shell program "rm *". This makes "<>" dangerous to use carelessly.

       context Produces a warning whenever an array is used in an implicit scalar context. For
               example, both of the lines

                   $foo = length(@bar);
                   $foo = @bar;

               will elicit a warning. Using an explicit scalar() silences the warning. For
               example,

                   $foo = scalar(@bar);

       implicit-read and implicit-write
               These options produce a warning whenever an operation implicitly reads or
               (respectively) writes to one of Perl's special variables.  For example, implicit-
               read will warn about these:

                   /foo/;

               and implicit-write will warn about these:

                   s/foo/bar/;

               Both implicit-read and implicit-write warn about this:

                   for (@a) { ... }

       bare-subs
               This option warns whenever a bareword is implicitly quoted, but is also the name
               of a subroutine in the current package. Typical mistakes that it will trap are:

                   use constant foo => 'bar';
                   @a = ( foo => 1 );
                   $b{foo} = 2;

               Neither of these will do what a naive user would expect.

               Notice: Perl 5.22.0 does not report "foo" in $b{foo} as BARE token anymore.
               Therefore B::Lint test is not reliable here. See CPAN RT#101115
               <https://rt.cpan.org/Public/Bug/Display.html?id=101115>.

       dollar-underscore
               This option warns whenever $_ is used either explicitly anywhere or as the
               implicit argument of a print statement.

       private-names
               This option warns on each use of any variable, subroutine or method name that
               lives in a non-current package but begins with an underscore ("_"). Warnings
               aren't issued for the special case of the single character name "_" by itself
               (e.g. $_ and @_).

       undefined-subs
               This option warns whenever an undefined subroutine is invoked.  This option will
               only catch explicitly invoked subroutines such as "foo()" and not indirect
               invocations such as "&$subref()" or "$obj->meth()". Note that some programs or
               modules delay definition of subs until runtime by means of the AUTOLOAD mechanism.

       regexp-variables
               This option warns whenever one of the regexp variables "$`", $& or "$'" is used.
               Any occurrence of any of these variables in your program can slow your whole
               program down. See perlre for details.

       all     Turn all warnings on.

       none    Turn all warnings off.

NON LINT-CHECK OPTIONS

       -u Package
               Normally, Lint only checks the main code of the program together with all subs
               defined in package main. The -u option lets you include other package names whose
               subs are then checked by Lint.

EXTENDING LINT

       Lint can be extended by with plugins. Lint uses Module::Pluggable to find available
       plugins. Plugins are expected but not required to inform Lint of which checks they are
       adding.

       The "B::Lint->register_plugin( MyPlugin => \@new_checks )" method adds the list of
       @new_checks to the list of valid checks. If your module wasn't loaded by Module::Pluggable
       then your class name is added to the list of plugins.

       You must create a "match( \%checks )" method in your plugin class or one of its parents.
       It will be called on every op as a regular method call with a hash ref of checks as its
       parameter.

       The class methods "B::Lint->file" and "B::Lint->line" contain the current filename and
       line number.

         package Sample;
         use B::Lint;
         B::Lint->register_plugin( Sample => [ 'good_taste' ] );

         sub match {
             my ( $op, $checks_href ) = shift @_;
             if ( $checks_href->{good_taste} ) {
                 ...
             }
         }

TODO

       while(<FH>) stomps $_
       strict oo
       unchecked system calls
       more tests, validate against older perls

BUGS

       This is only a very preliminary version.

AUTHOR

       Malcolm Beattie, mbeattie@sable.ox.ac.uk.

ACKNOWLEDGEMENTS

       Sebastien Aperghis-Tramoni - bug fixes