Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

BEGIN { push ( @INC, '/usr/local/lib/perl/5.14.2/File/') } #!/usr/bin/perl use File::Basename; use File::Spec::Functions; use Data::Dumper; use diagnostics; use warnings; use strict; my $data = data_for_path('/root/excerise_perl/test'); #print Dumper($data); sub data_for_path { my ($path) = @_; my $data = {}; my @queue = ([$path, $data]); while (my $next = shift @queue) { my($path, $ref ) = @$next; my $basename = basename ($path); $ref->{$basename} = do { if (-f $path or -l $path) {undef} else { my $hash = {}; opendir ((my $dh) , $path); my @new_paths =map { catfile ($path , $_) } grep {! /^\.\.?\z/ } readdir $dh; unshift @queue , map {[$_, $hash]} @new_paths; $hash; } }; } $data; }

this script is used to print one directory structure. if it is a file, then this values would be "undef", if it is a directory, it would be the hash reference for its child directory. now I run this script in my pc, the result is as below: root@TestMachine:~/excerise_perl# perl $VAR1 = { 'test' => { 'file2' => undef, 'file1' => undef, 'dir1' => { 'file3' => undef } } }; the directory have two files named "file1" and "file2", one director named "dir1" that has only one file named "file3". I can't understand this sentence "unshift @queue , map {$_, $hash} @new_paths;" the $hash seems not to be assigned a value, but why is $hash returned? what thing does "map {$_, $hash} @new_paths"? someone can help me to understand this script? thanks a lot!!