# Referensi Cepat Perl

*Variabel, regex, file I/O, referensi, dan modul esensial*

> Source: Perl Documentation (perldoc.perl.org) · MIT

## Dasar

### Hello World

```
#!/usr/bin/perl
use strict;
use warnings;
print "Hello, World!\n";
say "Hello, World!";  # dengan use feature 'say';
```

### Jalankan Perl

```
perl script.pl           # jalankan file
perl -e 'print "hi\n"'  # jalankan inline
perl -ne 'print' file   # proses file baris per baris
```

### Komentar & Dokumentasi

```
# komentar satu baris
=pod
Dokumentasi POD multi-baris
=cut
```

## Variabel

### Sigil

| Command | Description |
|---------|-------------|
| `$scalar` | Nilai tunggal (string, angka, referensi) |
| `@array` | Daftar scalar berurutan |
| `%hash` | Pasangan key-value |
| `$array[0]` | Akses satu elemen array (konteks scalar) |
| `$hash{key}` | Akses satu nilai hash (konteks scalar) |

### Variabel Scalar

```
my $name = "Perl";        # string
my $version = 5.40;       # angka
my $count = 42;           # integer
my $undef;                # tidak terdefinisi (undef)
my $combined = "$name v$version";  # interpolasi
```

### Konteks

```
my @arr = (1, 2, 3);
my $count = @arr;          # konteks scalar: 3
my @copy = @arr;           # konteks list: (1, 2, 3)
my $len = scalar @arr;     # paksa konteks scalar
```

### Variabel Spesial

| Command | Description |
|---------|-------------|
| `$_` | Variabel default (topik) |
| `@_` | Argumen subrutin |
| `$!` | Pesan error sistem |
| `$@` | Error dari eval |
| `$0` | Nama program |
| `@ARGV` | Argumen command-line |
| `%ENV` | Variabel environment |

## Operator

### Operator Perbandingan

| Command | Description |
|---------|-------------|
| `==, !=, <, >, <=, >=` | Perbandingan numerik |
| `eq, ne, lt, gt, le, ge` | Perbandingan string |
| `<=>` | Spaceship numerik (mengembalikan -1, 0, 1) |
| `cmp` | Spaceship string |
| `=~` | Cocokkan / bind regex |
| `!~` | Kecocokan regex dinegasikan |

### Operator String

```
my $full = "Hello" . " " . "World";  # penggabungan
my $line = "-" x 40;                  # pengulangan
my $len = length($full);              # 11
```

### Operator Logika

| Command | Description |
|---------|-------------|
| `&& / and` | AND logika (prioritas rendah: `and`) |
| `\|\| / or` | OR logika (prioritas rendah: `or`) |
| `// ` | Defined-or (mengembalikan kiri jika terdefinisi) |
| `! / not` | NOT logika |
| `? :` | Kondisional ternary |

## Alur Kontrol

### Kondisional

```
if ($x > 0) { print "positif\n"; }
elsif ($x == 0) { print "nol\n"; }
else { print "negatif\n"; }
print "ya\n" if $condition;     # if postfix
print "tidak\n" unless $condition;  # unless postfix
```

### Loop

```
for my $i (0..9) { print "$i\n"; }
foreach my $item (@array) { print "$item\n"; }
while ($line = <STDIN>) { chomp $line; }
until ($done) { last if check(); }
```

### Kontrol Loop

| Command | Description |
|---------|-------------|
| `next` | Lanjut ke iterasi berikutnya (seperti `continue`) |
| `last` | Keluar dari loop (seperti `break`) |
| `redo` | Mulai ulang iterasi saat ini |
| `next LABEL` | Lanjut ke iterasi berikutnya pada loop berlabel |
| `last LABEL` | Keluar dari loop berlabel |

### Given / When

```
use feature 'switch';
given ($status) {
    when ("ok")    { say "sukses"; }
    when ("error") { say "gagal"; }
    default        { say "tidak diketahui"; }
}
```

## Subrutin

### Subrutin Dasar

```
sub greet {
    my ($name) = @_;
    return "Hello, $name!";
}
my $msg = greet("Alice");
```

### Parameter Default & Named

```
sub connect {
    my (%opts) = @_;
    my $host = $opts{host} // "localhost";
    my $port = $opts{port} // 5432;
    return "$host:$port";
}
connect(host => "db.example.com", port => 3306);
```

### Referensi Subrutin

```
my $double = sub { return $_[0] * 2; };
print $double->(5);   # 10
my @sorted = sort { $a <=> $b } @nums;
```

### Prototipe & Signature

```
use feature 'signatures';
sub add($a, $b) { return $a + $b; }
sub greet($name, $greeting = "Hello") {
    return "$greeting, $name!";
}
```

## Regex

### Pencocokan

```
if ($str =~ /pattern/) { print "cocok\n"; }
if ($str =~ /(\d+)/) { print "angka: $1\n"; }
my @matches = ($str =~ /(\w+)/g);  # semua kecocokan
```

### Substitusi

```
$str =~ s/old/new/;      # kemunculan pertama
$str =~ s/old/new/g;     # global (semua kemunculan)
$str =~ s/^\s+|\s+$//g;  # trim whitespace
(my $clean = $str) =~ s/\W//g;  # salinan non-destruktif
```

### Modifier

| Command | Description |
|---------|-------------|
| `/i` | Case-insensitive |
| `/g` | Global (semua kecocokan) |
| `/m` | Multi-baris (`^` dan `$` cocok dengan batas baris) |
| `/s` | Satu baris (`.` cocok dengan newline) |
| `/x` | Extended (izinkan whitespace dan komentar) |

### Pola Umum

| Command | Description |
|---------|-------------|
| `\d, \D` | Digit / non-digit |
| `\w, \W` | Karakter kata / non-kata |
| `\s, \S` | Whitespace / non-whitespace |
| `\b` | Batas kata |
| `(?: ... )` | Grup non-capture |
| `(?<name> ... )` | Capture bernama (akses via `$+{name}`) |

## File I/O

### Buka & Baca

```
open(my $fh, '<', 'data.txt') or die "Tidak bisa buka: $!";
while (my $line = <$fh>) {
    chomp $line;
    print "$line\n";
}
close($fh);
```

### Tulis & Tambahkan

```
open(my $fh, '>', 'out.txt') or die "Tidak bisa buka: $!";
print $fh "Hello\n";
close($fh);
open(my $fh, '>>', 'log.txt') or die "Tidak bisa buka: $!";
print $fh "entry\n";
close($fh);
```

### Slurp Seluruh File

```
use File::Slurp;
my $content = read_file('data.txt');
my @lines = read_file('data.txt', chomp => 1);
```

### Uji File

| Command | Description |
|---------|-------------|
| `-e $path` | File ada |
| `-f $path` | Adalah file biasa |
| `-d $path` | Adalah direktori |
| `-r / -w / -x` | Dapat dibaca / ditulis / dieksekusi |
| `-s $path` | Ukuran file dalam byte (0 jika kosong) |
| `-z $path` | File berukuran nol |

## Array & Hash

### Array

```
my @arr = (1, 2, 3, 4, 5);
push @arr, 6;              # tambahkan ke akhir
my $last = pop @arr;       # hapus elemen terakhir
my $first = shift @arr;    # hapus elemen pertama
unshift @arr, 0;           # tambahkan ke depan
my @slice = @arr[1..3];    # slice
```

### Fungsi Array

| Command | Description |
|---------|-------------|
| `scalar @arr` | Jumlah elemen |
| `push / pop` | Tambah/hapus dari akhir |
| `shift / unshift` | Hapus/tambah dari awal |
| `splice(@a, 2, 1)` | Hapus 1 elemen pada indeks 2 |
| `sort @arr` | Urutkan secara alfabetis |
| `reverse @arr` | Balik urutan |
| `grep { /pat/ } @arr` | Filter berdasarkan pola |
| `map { $_ * 2 } @arr` | Transformasi setiap elemen |
| `join(',', @arr)` | Gabungkan menjadi string |

### Hash

```
my %user = (name => "Alice", age => 30);
$user{email} = "a\@b.com";    # tambah pasangan
delete $user{age};             # hapus pasangan
my @keys = keys %user;
my @vals = values %user;
```

### Iterasi Hash

```
while (my ($k, $v) = each %hash) {
    print "$k => $v\n";
}
for my $key (sort keys %hash) {
    print "$key: $hash{$key}\n";
}
```

## Referensi

### Membuat Referensi

```
my $scalar_ref = \$name;
my $array_ref  = \@arr;
my $hash_ref   = \%hash;
my $anon_arr   = [1, 2, 3];       # referensi array anonim
my $anon_hash  = {a => 1, b => 2}; # referensi hash anonim
```

### Dereference

```
print $$scalar_ref;          # dereference scalar
print $array_ref->[0];       # notasi panah
print $hash_ref->{key};      # notasi panah
my @copy = @$array_ref;      # dereference ke array
my %copy = %$hash_ref;       # dereference ke hash
```

### Struktur Data Kompleks

```
my @users = (
    { name => "Alice", age => 30 },
    { name => "Bob",   age => 25 },
);
print $users[0]->{name};   # "Alice"
```

### Fungsi ref()

| Command | Description |
|---------|-------------|
| `ref($r) eq 'SCALAR'` | Referensi ke scalar |
| `ref($r) eq 'ARRAY'` | Referensi ke array |
| `ref($r) eq 'HASH'` | Referensi ke hash |
| `ref($r) eq 'CODE'` | Referensi ke subrutin |

## Modul

### Menggunakan Modul

```
use strict;
use warnings;
use List::Util qw(sum max min);
use File::Basename;
use Cwd qw(abs_path);
```

### Membuat Modul

```
# MyModule.pm
package MyModule;
use Exporter 'import';
our @EXPORT_OK = qw(helper);
sub helper { return "help"; }
1;  # modul harus mengembalikan true
```

### Modul Core Umum

| Command | Description |
|---------|-------------|
| `List::Util` | sum, max, min, reduce, any, all |
| `File::Basename` | basename, dirname, fileparse |
| `File::Path` | make_path, remove_tree |
| `Getopt::Long` | Parsing opsi command-line |
| `JSON` | encode_json, decode_json |
| `LWP::Simple` | get($url) — HTTP client sederhana |
| `Data::Dumper` | Debug dump struktur data |
| `Carp` | croak, confess — pesan error lebih baik |

### CPAN

```
cpan install Module::Name        # install dari CPAN
cpanm Module::Name               # cpanminus (lebih cepat)
perldoc Module::Name             # baca dokumentasi modul
```