Programming Perl, 4th Edition

Multiplicative Operators

Perl provides the C-like operators * (multiply), / (divide), and % (modulo). The * and / work exactly as you would expect, multiplying or dividing their two operands. Division is done in floating point, unless you’ve used any of the integer, bigint, bigrat, or bignum pragmatic modules. The % operator converts its operands to integers before finding the remainder according to integer division. (However, it does this integer division in floating point if necessary, so your operands can be up to 15 digits long on most 32-bit machines.) Assume that your two operands are called $a and $b. Unlike a mathematical remainder function, Perl’s % operator defines a sawtooth function on the real number line that drops to 0 at the origin and at every multiple of the divisor, ramping up to just under the divisor within each divisor interval. Unlike a remainder function, it is not symmetric around 0, but continues the sawtooth pattern on both sides of 0. Mathematically, $a % $b is therefore:

$a % $b == $a - ( POSIX::floor($a / $b) * $b )

When use integer is in scope, % gives you direct access to the modulus operator as implemented by your C compiler. This operator is not well defined for negative operands, but it will execute faster.

Binary x is the repetition operator. Actually, it’s two operators. In scalar context, it returns a concatenated string consisting of the left operand repeated the number of times specified by the right operand. (For backward compatibility, it also ...