Perl Data Types

Perl is a weakly typed language, so variables do not need to specify a type. The Perl interpreter automatically selects the matching type based on the context.

Perl has three basic data types: scalars, arrays, and hashes. The following is a description of these three data types:

Number Type and Description
1 Scalar

A scalar is the simplest data type in Perl. Variables of this data type can be numbers, strings, or floating-point numbers, with no strict distinction. When using it, add a$before the variable name to indicate that it is a scalar. For example:

$myfirst=123;　    #数字123　

$mysecond="123";   #字符串123　
2 Array

Array variables use the character@at the beginning, with indices starting from 0, for example:@arr=(1,2,3)

@arr=(1,2,3)
3 Hash

A hash is an unorderedkey/valuepair collection. You can use keys as subscripts to obtain values. Hash variables use the character%at the beginning.

%h=('a'=>1,'b'=>2);

Numeric Literals

1. Integer

Perl actually stores integers in the floating-point registers of your computer, so they are actually treated as floating-point numbers.

On most computers, floating-point registers can store about 16 digits; anything longer than this is discarded. Integers are actually a special case of floating-point numbers.

Integer variables and operations:

$x = 12345;
if (1217 + 116 == 1333) {
    # 执行代码语句块
}

Octal and hexadecimal numbers: octal numbers start with 0, hexadecimal numbers start with 0x. For example:

$var1 = 047;    # 等于十进制的39
$var2 = 0x1f;   # 等于十进制的31

2. Floating Point Numbers

Floating-point data such as: 11.4, -0.3, .3, 3., 54.1e+02, 5.41e03.

Floating-point registers usually cannot store floating-point numbers precisely, which causes errors. Special attention should be paid during operations and comparisons. The exponent range is usually -309 to +308.

Example

#!/usr/bin/perl $value = 9.01e+21 + 0.01 - 9.01e+21; print ("The first value is:", $value, "\n"); $value = 9.01e+21 - 9.01e+21 + 0.01; print ("The second value is:", $value, "\n");

After executing the above program, the output is:

第一个值为：0
第二个值为:0.01

3. Strings

Strings in Perl are represented using a scalar. The way to define them is very similar to C, but in Perl, strings are not terminated with \0.

The difference between double quotes and single quotes in Perl: Double quotes can properly parse some escape characters and variables, while single quotes cannot parse them and will output them as-is.

However, using single quotes allows multi-line text, as shown below:

#!/usr/bin/perl 

$var='这是一个使用

多行字符串文本

的例子';

print($var);

After executing the above program, the output is:

This is an example of using

multi-line string text

Some common escape characters in Perl are shown in the table below:

Escape Character Meaning
\\ Backslash
\' Single quote
\" Double quote
\a System bell
\b Backspace
\f Form feed
\n Newline
\r Carriage return
\t Horizontal tab
\v Vertical tab
\0nn Creates a number in octal format
\xnn Creates a number in hexadecimal format
\cX Control character; x can be any character
\u Forces the next character to uppercase
\l Forces the next character to lowercase
\U Forces all characters to uppercase
\L Forces all characters to lowercase
\Q Adds a backslash to non-word characters up to \E
\E Ends \L, \U, \Q

Example

Next, let's take a detailed look at the use of single quotes, double quotes, and escape characters:

Example

#!/usr/bin/perl # Newline \n inside double quotes is effective $str = "Example\nwww.example.com"; print "$str\n"; # Newline \n inside single quotes is ineffective $str = 'Example \nwww.example.com'; print "$str\n"; # Only R will be converted to uppercase $str = "\uexample"; print "$str\n"; # All letters will be converted to uppercase $str = "\Uexample"; print "$str\n"; # The specified parts will be converted to uppercase $str = "Welcome to \Uexample\E.com!"; print "$str\n"; # Adds a backslash to non-word characters up to \E $str = "\QWelcome to example's family"; print "$str\n";

The output of the above example is:

Other Extensions