A.4 Assignment

Scalar variables are assigned scalar values with an assignment operator (the equals sign) in an assignment statement:

 $thousand = 1000; 

assigns the integer 1000, a scalar value, to the scalar variable $thousand .

The assignment statement looks like an equal sign from elementary mathematics, but its meaning is different. The assignment statement is an instruction, not an assertion. It doesn't mean " $thousand equals 1000." It means "store the scalar value 1000 into the scalar variable $thousand ". However, after the statement, the value of the scalar variable $thousand is, indeed, equal to 1000.

References are usually saved in scalar variables. For example:

 $pi = .14159265; 

If you try to print $pi after this assignment, you get an indication that it's a reference to a scalar value at a memory location represented in hexadecimal digits. To print the value of a variable that's a reference to a scalar, precede its name with an additional dollar sign:

 print $pi,"\n"; print $$pi, "\n"; 

This gives the output:

 SCALAR(0x811d1bc) 3.14159265 

You can assign values to several scalar variables by surrounding variables and values in parentheses and separating them by commas, thus making lists:

 ($one, $two, $three) = ( 1, 2, 3); 

There are several assignment operators besides = that are shorthand for longer expressions. For instance, $a += $b is equivalent to $a = $a + $b . Table A-1 is a complete list.

Table A-1. Assignment operator shorthands

Example of operator	Equivalent
$a += $b	$a = $a + $b	(addition)
$a -= $b	$a = $a - $b	(subtraction)
$a *= $b	$a = $a * $b	(multiplication)
$a /= $b	$a = $a / $b	(division)
$a **= $b	$a = $a ** $b	(exponentiation)
$a %= $b	$a = $a % $b	(remainder of $a / $b)
$a x= $b	$a = $a x $b	(string $a repeated $b times)
$a &= $b	$a = $a & $b	(bitwise AND)
$a = $b	$a = $a $b	(bitwise OR)
$a ^= $b	$a = $a ^ $b	(bitwise XOR)
$a >>= $b	$a = $a >> $b	($a shift $b bits)
$a <<= $b	$a = $a >> $b	($a shift $b bits to left)
$a &&= $b	$a = $a && $b	(logical AND)
$a = $b	$a = $a $b	(logical OR)
$a .= $b	$a = $a . $b	(append string $b to $a)