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Editor to share with you how to use the Perl operator, I believe that most people do not know much about it, so share this article for your reference, I hope you can learn a lot after reading this article, let's learn about it!

Arrow Perl operator

Like C and C++, the binocular Perl operator-> is an infix dereferencing Perl operator. If on the right is a [...] Array subscript, a {.} hash subscript, or a (.) A list of subprocedure parameters, then on the left must be a corresponding array, hash, or application of the subprocedure (hard reference or symbolic reference). In a left value (assignable) environment, if the left side is not a reference, it must be a location that can hold hard references, in which case the reference will be automatically activated for you. For more information on this (and some warnings about intentional self-activation), see Chapter 8, references.

$aref- > [42] # an array dereference

$href- > {"cornedbeff"} # A hash dereference

$sref- > (1, 2, 3) # dereference of a sub-procedure

Otherwise, it is some kind of method call. On the right must be a method name (or a simple scalar variable containing the method name), and the left must come up with an object name (a blessed reference) or a class name (that is, a package name):

$yogi=Bear- > new ("Yogi"); # A class method call $yogi- > swipe ($picnic); # an object method call

The method name can be modified with a package name to indicate which package to start searching for the method, or with a special package name, SUPER::, to indicate that the search should start with the parent class. See Chapter 12, objects.

Self-increment and self-subtraction Perl operators

The + + and-- Perl operators function the same as in C. That is, when they are placed in front of a variable, they increase or decrease the value of the variable before returning the value of the variable, and when placed after the variable, they add or subtract one to the value of the variable after it is returned. For example, $asides + increments the value of the scalar variable $an and returns its value before it performs the increment. Similarly,-- $b {(/ (\ w+) /) [0]} subtracts the elements in the hash% b indexed by * words in the default search variable ($_) by one and then returns. Note: Oh, it may be a little unfair here, because there are a lot of things you don't know yet. We just want you to focus. The expression works like this: first, pattern matching uses the expression\ w + to find * words in $_. The parentheses around it ensure that the word is returned as a single element list value, because the pattern matching takes place in the list environment. This list environment is provided by the list fragment Perl operator, (...) [0], which returns * (also * one) elements of the list. The value is used as a hash key, and then the hash record (value) is judged and returned. Usually, if you come across a complex expression, you can analyze it from the inside out and find out the order in which things happen. )

The self-incrementing Perl operator has a little extra built-in processing. If the variable you add is a number, or if the variable is used in a digital environment, you get the normal self-increment function. However, if the variable is always used in a string environment and the value is non-empty and matches the pattern / ^ [a-zA-z] * [0-9] * $/, then the self-increment is carried out as a string, each character remains in its range and carries:

Print++ ($foo='99'); # print '100'

Print++ ($foo='a0'); # print 'a1'

Print++ ($foo='Az'); # print 'Ba'

Print++ ($foo='zz'); # print 'aaa'

As we write this, the self-added extra processing has not been extended to Unicode characters and numbers, but it may be in the future.

However, the self-subtractive Perl operator has no additional processing, and we are not prepared to add this processing to it.

Exponential operation

Binocular * * is an exponential Perl operator. Note that it is even more stringent than the bindings of the monocular Perl operator, so-2 is 4 is-(2) 4, not (- 2) * 4. This Perl operator is implemented using C's pow (3) function, which operates internally in floating-point mode. It uses logarithmic operations, which means it can handle decimal exponents, but sometimes the results you get are not as accurate as those obtained directly by multiplication.

Ideographic monocular Perl operator

Most unary Perl operators have only names (see "named monocular and file test Perl operators" later in this chapter), but some Perl operators are considered important, so they give them their own special symbols. All such Perl operators seem to have something to do with negative operations. Scold mathematicians.

Monocular! Execute logic no, that is, "not". Refer to not to see whether or not a logic is lower in priority. If the Operand is false (numeric zero, string "0", empty string or undefined), the value is true (1), and if the Operand is true, the value is false ("").

If the Operand is a number, monomial-performs mathematical negatives. If the Operand is an identity, returns a string concatenated by a negative sign and an identifier. Otherwise, if the string begins with a positive or negative sign, the string that begins with the opposite sign is returned. One effect of these rules is that-bareword equals "- bareword". This is very useful for Tk programmers.

The monomial ~ Perl operator performs bitwise inversion, that is, the complement of 1. By definition, this is something that is not portable because it is limited by your machine. For example, on a 32-bit machine, ~ 123 is 4294967172, while on a 64-bit machine, it is 18446744073709551493. But you already know that.

What you may not know is that if the argument to ~ is a string instead of a number, an equal length string is returned, but all the bits of the string are complementary. This is the fastest way to flip all bits at the same time, and it's also a portable way to flip bits, because it doesn't depend on the word size of your machine. We'll talk about the bitwise logic Perl operator later, which also has a string-oriented variant.

Monomial + has no semantic effect, even for strings. It is used syntactically to separate the function name from a parenthesized expression, otherwise they will be interpreted as one function parameter. (see "item and list Perl operators" for an example. If you think about it on one side, + cancels the effect of parentheses turning the prefix Perl operator into a function.

The unary Perl operator\ creates a reference to what follows it. When used on a list, it creates a list of references. See "backslash Perl operator" in Chapter 8 for more information. Don't confuse this property with the function of the backslash in the string, although both have vague meanings to prevent the next thing from being converted. Of course, this similarity is not entirely accidental.

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