Programming Perl, 4th Edition

Some Numeric and String Comparison Operators

Comparison, or relational, operators tell us how two scalar values (numbers or strings) relate to each other. There are two sets of operators: one does numeric comparison and the other does string comparison. (In either case, the arguments will be “coerced” to have the appropriate type first.) Assuming left and right arguments of $a and $b, Table 1-5 shows us what we have.

Table 1-5. Comparison operators

Comparison	Numeric	String	Return Value
Equal	==	eq	True if $a is equal to $b
Not equal	!=	ne	True if $a is not equal to $b
Less than	<	lt	True if $a is less than $b
Greater than	>	gt	True if $a is greater than $b
Less than or equal	<=	le	True if $a not greater than $b
Greater than or equal	>=	ge	True if $a not less than $b
Comparison	<=>	cmp	0 if equal, 1 if $a greater, −1 if $b greater

The last pair of operators (<=> and cmp) are entirely redundant with the earlier operators. However, they’re incredibly useful in sort subroutines (see Chapter 27).^[27]

^[27] Some folks feel that such redundancy is evil because it keeps a language from being minimalistic, or orthogonal. But Perl isn’t an orthogonal language; it’s a diagonal language. By this we mean that Perl doesn’t force you to always go at right angles. Sometimes you just want to follow the hypotenuse of the triangle to get where you’re going. TMTOWTDI is about shortcuts. Shortcuts are about programmer efficiency.