In

Perl, a comparison

operator for numbers, similar to the string comparison operator '

cmp'.

<=> and cmp return:

These returns are the same as

strcmp in

C.

The <=> operand is known as the spaceship operator, for reasons that should be obvious if you have seen Star Wars.

In

maths (esp.

logic), "<=>" means

double implication, an

implication that goes both ways. In other words,

A <=> B

means the same as

A => B **and** B => A

"<=>" is often read as "if and only if".