ch02.047_best

Perl Best Practices the source code

##############################################################################
##   Code fragment (Recommended) from Chapter 2 of "Perl Best Practices"    ##
##     Copyright (c) O'Reilly & Associates, 2005. All Rights Reserved.      ##
##  See: http://www.oreilly.com/pub/a/oreilly/ask_tim/2001/codepolicy.html  ##
##############################################################################


# Standard modules...
use strict;
use warnings;
use IO::Prompt;
use Carp;
use English qw( -no_match_vars );
use Data::Alias;
use Readonly;

Readonly my $EMPTY_STR => q{};

my $sigil    = '$';
my $subsigil = '?';
my $var_name = '$?foo';
my $var_ref;

my $internal_count;
my $external_count;
my %has_internal;
my %has_external;

my %sym_table = ( $var_name => 42 );

if ($sigil eq '$') {
    if ($subsigil eq '?') {                        
        $sym_table{ substr($var_name,2) } = delete $sym_table{$var_name};
 
        $internal_count++;
        $has_internal{$var_name}++;

    }
    else {
        ${$var_ref} = q{$sym_table{$var_name}};
 
        $external_count++;
        $has_external{$var_name}++;
    }
}
elsif ($sigil eq '@' && $subsigil eq '?') {
    @{ $sym_table{$var_name} } 
        = grep {defined $_} @{$sym_table{$var_name}};
}
elsif ($sigil eq '%' && $subsigil eq '?') {
    delete $sym_table{$var_name}{$EMPTY_STR};
}
else {
    ${$var_ref} = q{$sym_table{$var_name}};
}

use Data::Dumper 'Dumper';
warn Dumper [ \%sym_table ];