NAME PerlX::ScopeFunction - new keywords for creating scopes. SYNOPSIS use List::MoreUtils qw( part ); use PerlX::ScopeFunction qw( let with ); with ( part { $_ % 2 } @input ) { my ($evens, $odds) = @_; say "There are " . scalar(@$evens) . " even numbers: " . join(" ", @$evens); say "There are " . scalar(@$odds) . " odd numbers: " . join(" ", @$odds); } let ($max = max(@input)) { ... } DESCRIPTION Scope functions can be used to create small lexical scope, inside which the results of an given expression are used, but not outside. This module provide 2 extra keywords -- with and let -- for creating creating scopes that look a little bit better than just a bare code BLOCK. By use-ing this module without a import list, all keywords are imported. To import only wanted keywords, specify them in the import list: # Import all keywords use PerlX::ScopeFunction; # Import just `let` use PerlX::ScopeFunction qw(let); # Import just `with`, and name it differently use PerlX::ScopeFunction 'with' => { -as 'withThese' } Imported keywords can be removed by a no statement. no PerlX::ScopeFunction; with The with keyword can be used to bring the result of an given EXPR to a smaller scope (code block): with ( EXPR ) BLOCK The EXPR are evaluated in list context, and the result (a list) is available inside BLOCK as @_. The conventional topic variable $_ is also assigned the last value of the list ($_[-1]). let The let keyword can be used to create locally readonly variables in a smaller scope (code block). The keyword let should be followed by a list of assignment expressions, then a block. let ( ASSIGNMENTS ) BLOCK The ASSIGNMENTS means a list of assignment statements seperated by semicolons, and the operator must =. They are evalutade in the same order as they are defined and becomes new, readyonly, variables are inside the BLOCK. Variables created in the beginning of this list of can be used in the latter positions. If in the current scope, thee are variables with identical names as the LHS in the ASSIGNMENTS, they are masked in the let-block. For example, these would creating 3 new variables in the let-block that mask the ones with identical names in the current scope. my ($foo, $bar, $baz) = (10, 20, 30); let ($foo = 1; $bar = 2; $baz = $foo + $bar) { say "$foo $bar $baz"; #=> 1 2 3 } say "$foo $bar $baz"; #=> 10 20 30 Array and Hashes can also be created this way: let (@foo = (1,2,3); %bar = (bar => 1); $baz = 42) { ... } Importing as different names Since the keywords provided in this module are commonly defined in other CPAN modules, this module also provides a way to let users to import those keywords as different name, with a conventional spec also seen in Sub::Exporter. For example, to import with as given_these, you say: use PerlX::ScopeFunction "with" => { -as => "given_these" }; Basically whenever there is a HashRef in the import list, previous entries is imported. But "-as" is the only meaningful key. All other options seen in Sub::Exporter are ignored. CAVEATS Due to the fact this module hooks into perl parser, the keywords cannot be used without being imported into current namespace. Statements like the following does not compile: PerlX::ScopeFunction::let( ... ) { ... } PerlX::ScopeFunction::with( ... ) { ... } AUTHOR Kang-min Liu LICENCE The MIT License DISCLAIMER OF WARRANTY BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR, OR CORRECTION. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.