NAME

Keyword::Value -- assign a constant to a variable or symbol.

SYNOPSIS

    # "value" takes either a variable definition and expression
    # or an expression. the result is locked using Data::Lock.

    use Keyword::Value;    

    value my    $foo    = 'bar';
    value our   $bletch = 'blort';
    value state $bim    = 'bam';
    value       %::blah = ( 'a' .. 'z' );
    value my    @stuff  = ( 1 .. 100 );

    # default is to create a lexical variable if the 
    # variable name lacks '::'.
    #
    # these have identical results in the code:

    value   my $a = 'b';
    value      $a = 'b';

    # at this point modification via assignment to the 
    # variable or sub-parts, undef, delete, push, pop, or
    # assignment to a new key/offset will with an error
    # about modifying a read-only value, disallowed key,
    # readonly offset, or readonly key.

    sub foo
    {
        # return a constant value to the caller.

        value sha256 @_
    }

    # carp if the constant value is undef.

    $ENV{ VERBOSE_KEYWORD_VALUE } = 1;

DESCRIPTION

This module installs a "value" keyword which can be used to create constant-valued varabies in Perl5. The "value" keyword can be applied to simple scalars, nested structures such as arrays or hashes, or the return value of subroutine calls.

SEE ALSO

Data::Lock

This is where the locking mechanism comes from, and includes an unlock (useful for debugging and testing) and description of how the locks work.

perldoc perlsub

Use of ":lvalue" used in local sub to actually perform the locking.

AUTHOR

Steven Lembark <lembark@wrkhors.com>

LICENSE

This code is licensed under the same terms as Perl-5.22 or any later version of Perl.