Scalars and Operators

my $name = "Ada";
my $count = 42;
my $pi = 3.14159;
my $missing = undef;

defined $missing;           # false

my $lit = 'literal $name';   # no interpolation except backslash and quote rules
my $str = "Hello, $name\n"; # variables and escapes interpolate
my $sq = q{single quote style};
my $dq = qq{double quote style $name};

my $email = <<~EOT;          # ~ strips leading indentation (Perl 5.26+)
    Dear $name,
    Your total is $count.
    EOT

my $raw = <<~'EOT';          # single-quoted terminator: no interpolation
    literal $name stays as-is
    EOT

$x + $y                     # add
$x - $y                     # subtract
$x * $y                     # multiply
$x / $y                     # divide
$x % $y                     # remainder
$x ** $y                    # exponent
++$x; $x--;                 # increment/decrement

$s . $t                     # concatenate
$s x 3                      # repeat string 3 times
length $s                   # character count
substr($s, 0, 3)            # substring
index($s, "needle")         # first index or -1
lc $s; uc $s;               # lower/upper case

sprintf "%05d", 42;             # 00042 (zero-pad to width 5)
sprintf "%8.2f", 3.14159;       # '    3.14' (width 8, 2 decimals)
sprintf "%-10s|", "left";       # 'left      |' (left-justify)
sprintf "%x %o %b", 255, 8, 5;  # ff 10 101 (hex, octal, binary)
sprintf "%e", 12345.678;        # 1.234568e+04
sprintf "%s%%", 99;             # 99% (literal percent sign)

if ($n == 10) { ... }       # numbers
if ($name eq "Ada") { ... } # strings

my $name = shift @ARGV // "world";     # fallback only if undef
my $port = $ENV{PORT} || 3000;          # fallback for any false value
$hash{count} //= 0;                     # assign default if undef