Hello Monks,

I am trying to enlighten myself by reading as much code on here as possible and figuring out the parts that I do not understand. I came across this post Networking Perl today and Your Mother's reply had the following code

use warnings;
use strict;
use JSON;
use Plack::Request;
use Proc::ProcessTable;

sub {
    my $req = Plack::Request->new(+shift);
    my %pids = map { $_ => 1 } $req->path =~ /(\d+)/g;

    my $procs = Proc::ProcessTable->new;
    my $json = JSON->new;

    my %status;
    for my $proc ( @{ $procs->table } )
    {
        next if scalar(%pids) and not $pids{$proc->pid};

        for my $field ( $procs->fields )
        {
            $status{$proc->pid}{$field} = $proc->$field;
        }
    }

    return [ 200,
             [ "Content-Type" => "application/json" ],
             [ $json->pretty->encode(\%status) ]
             ];

};
[download]

There are two items in this that are giving me trouble. First this map, I don't quite understand what it is doing (it seems no matter how much I read about map I still can't quite grasp it):

my %pids = map { $_ => 1 } $req->path =~ /(\d+)/g;
[download]

Is it saying "For each item found in $req->path that is a number save it as a hash key of %pids?"

The other thing that confuses me is this

next if scalar(%pids) and not $pids{$proc->pid};
[download]

I know "scalar(%pids)" will force the hash %pids to be interpreted in scalar context, but to be honest with you I do not know exactly what this will do to the hash. I tried testing this on my own with the following code:

my %hash = (
        fred => flintstone,
        wilma => flintstone,
        barney => ruble,
        );

print scalar(%hash) . "\n";
[download]

But this prints out "3/8" so I'm really confused.

Thank you for helping me on my journey.

Thanks,
Dru

Perl, the Leatherman of Programming languages. - qazwart