逻辑运算符 #

my $a = 1;
my $b = 1;

if ($a && $b) {
    print "Both are true\n";
}

my $a = 1;
my $b = 1;

if ($a and $b) {
    print "Both are true\n";
}

my $x = 0;
my $y = 1;

if ($x && $y++) {
    print "True\n";
}
print "y = $y\n";

my $file = "test.txt";

if (-e $file && -r $file) {
    print "File exists and is readable\n";
}

my $a = 0;
my $b = 1;

if ($a || $b) {
    print "At least one is true\n";
}

my $a = 0;
my $b = 1;

if ($a or $b) {
    print "At least one is true\n";
}

my $x = 1;
my $y = 0;

if ($x || $y++) {
    print "True\n";
}
print "y = $y\n";

open my $fh, "<", "file.txt"
    or die "Cannot open file: $!";

my $value = $config{setting} // "default";

my $a = 0;

if (!$a) {
    print "a is false\n";
}

my $a = 0;

if (not $a) {
    print "a is false\n";
}

my $logged_in = 0;

if (!$logged_in) {
    print "Please log in\n";
}

my $a = 0;
my $b = 1;

my $result1 = $a && $b || 1;
my $result2 = $a and $b or 1;

print "result1 = $result1\n";
print "result2 = $result2\n";

if ($condition1 && $condition2) {
    do_something();
}

open my $fh, "<", $file or die "Cannot open: $!";

my $name;
my $display = $name // "Anonymous";
print $display;

my $value = 0;

my $result1 = $value || "default";
my $result2 = $value // "default";

print "||: $result1\n";
print "//: $result2\n";

my $config = {
    timeout => 30,
    retries => 0,
};

my $timeout = $config->{timeout} // 60;
my $retries = $config->{retries} // 3;
my $debug = $config->{debug} // 0;

print "timeout: $timeout\n";
print "retries: $retries\n";
print "debug: $debug\n";

my $a = 1;
my $b = 0;

if ($a xor $b) {
    print "Exactly one is true\n";
}

sub xor_custom {
    my ($a, $b) = @_;
    return ($a && !$b) || (!$a && $b);
}

my $condition = 1;
my $result = $condition ? "true" : "false";
print $result;

my $age = 20;
my $status = $age >= 18 ? "adult" : "minor";
print $status;

my $score = 85;
my $grade = $score >= 90 ? "A" :
            $score >= 80 ? "B" :
            $score >= 70 ? "C" :
            $score >= 60 ? "D" : "F";
print $grade;

my @false_values = (0, "0", "", undef, ());

foreach my $val (@false_values) {
    if ($val) {
        print "true\n";
    } else {
        print "false\n";
    }
}

my @true_values = (1, -1, "hello", " ", "0.0", []);

foreach my $val (@true_values) {
    if ($val) {
        print "true\n";
    }
}

#!/usr/bin/perl
use strict;
use warnings;
use v5.10;

my ($username, $password, $is_admin) = ("admin", "secret", 1);

if ($username eq "admin" && $password eq "secret") {
    say "Login successful";
    if ($is_admin) {
        say "Welcome, Administrator!";
    }
} else {
    say "Login failed";
}

#!/usr/bin/perl
use strict;
use warnings;
use v5.10;

my %config = (
    host => "localhost",
    port => 3306,
);

my $host = $config{host} // "127.0.0.1";
my $port = $config{port} // 80;
my $user = $config{user} // "root";
my $pass = $config{pass} // "";

say "Host: $host";
say "Port: $port";
say "User: $user";
say "Pass: " . ($pass ? "****" : "(empty)");

#!/usr/bin/perl
use strict;
use warnings;
use v5.10;

my @items = (1, 2, 3, 4, 5);

my $count = scalar @items;
my $message = $count == 0 ? "No items" :
              $count == 1 ? "One item" :
              "$count items";

say $message;

my @empty = ();
$count = scalar @empty;
$message = $count == 0 ? "No items" :
           $count == 1 ? "One item" :
           "$count items";

say $message;