this no one will understand

#!/usr/bin/env perl

# pyreg.pl: registry-style store that appears as a Unix directory tree (Perl version).

#

# Keys look like HKEY_CURRENT_USER\Software\MyApp and hold named values.

# The store lives in ~/.pyreg.json and is materialised as files under ~/pyreg/.

#

# Usage:

#   pyreg.pl set     <key> <name> <value>

#   pyreg.pl setfile <key> <name> <file>    store a script's source as a value

#   pyreg.pl get     <key> <name>

#   pyreg.pl run     <key> <name>           run a stored script (.py .pl .sh)

#   pyreg.pl list

#   pyreg.pl mount

use strict;

use warnings;

use JSON::PP;

use File::Path qw(make_path);

use File::Spec;

use File::Temp qw(tempfile);

my $home  = $ENV{HOME} or die "HOME not set\n";

my $store = "$home/.pyreg.json";

my $mount = "$home/pyreg";

my $json  = JSON::PP->new->canonical->pretty;

sub load {

    return {} unless -e $store;

    open my $fh, '<', $store or die "cannot read $store: $!\n";

    local $/;

    my $data = <$fh>;

    close $fh;

    return decode_json($data);

}

sub save {

    my ($reg) = @_;

    open my $fh, '>', $store or die "cannot write $store: $!\n";

    print $fh $json->encode($reg);

    close $fh;

}

sub key_path {

    my ($key) = @_;

    (my $k = $key) =~ s{/}{\\}g;

    my @parts = grep { length } split /\\/, $k;

    die "invalid key\n" if grep { $_ eq '..' || $_ eq '.' } @parts;

    return File::Spec->catdir(@parts);

}

sub do_mount {

    my ($reg) = @_;

    make_path($mount);

    for my $key (sort keys %$reg) {

        my $dir = File::Spec->catdir($mount, key_path($key));

        make_path($dir);

        for my $name (sort keys %{ $reg->{$key} }) {

            next if $name =~ m{/} || $name eq '.' || $name eq '..';

            my $path = "$dir/$name";

            open my $fh, '>', $path or die "cannot write $path: $!\n";

            print $fh $reg->{$key}{$name};

            close $fh;

            chmod 0755, $path if $name =~ /\.(py|pl|sh)$/;

        }

    }

    print "mounted at $mount\n";

}

my ($cmd, @a) = @ARGV;

unless (defined $cmd) { print "usage: $0 set|setfile|get|run|list|mount ...\n"; exit 0; }

my $reg = load();

if ($cmd eq 'set' && @a == 3) {

    $reg->{ $a[0] }{ $a[1] } = $a[2];

    save($reg);

    do_mount($reg);

}

elsif ($cmd eq 'setfile' && @a == 3) {

    open my $fh, '<', $a[2] or die "cannot read $a[2]: $!\n";

    local $/;

    $reg->{ $a[0] }{ $a[1] } = <$fh>;

    close $fh;

    save($reg);

    do_mount($reg);

}

elsif ($cmd eq 'get' && @a == 2) {

    print $reg->{ $a[0] }{ $a[1] } // '', "\n";

}

elsif ($cmd eq 'run' && @a == 2) {

    my $src = $reg->{ $a[0] }{ $a[1] };

    die "no such value\n" unless defined $src;

    my %interp = (py => 'python3', pl => 'perl', sh => 'bash');

    my ($ext) = $a[1] =~ /\.(\w+)$/;

    my $prog = $interp{ $ext // '' } or die "don't know how to run '$a[1]'\n";

    my ($fh, $tmp) = tempfile(SUFFIX => ".$ext", UNLINK => 1);

    print $fh $src;

    close $fh;

    system($prog, $tmp);

    exit($? >> 8);

}

elsif ($cmd eq 'list') {

    print $json->encode($reg);

}

elsif ($cmd eq 'mount') {

    do_mount($reg);

}

else {

    die "bad arguments; run with no arguments for usage\n";

}