Perl scalar
Scalar is a simple data elements.
Scalar can be an integer, floating point numbers, characters, strings, paragraphs or a complete page.
The following example demonstrates a simple scalar application:
#!/usr/bin/perl $age = 20; # 整数赋值 $name = "w3big"; # 字符串 $salary = 130.50; # 浮点数 print "Age = $age\n"; print "Name = $name\n"; print "Salary = $salary\n";
The above program, the output is:
Age = 20 Name = w3big Salary = 130.5
Digital scalar
Scalar usually a number or string, the following example demonstrates the use of different digital scalar types:
#!/usr/bin/perl $integer = 200; $negative = -300; $floating = 200.340; $bigfloat = -1.2E-23; # 八进制 377 , 十进制为 255 $octal = 0377; # 十六进制 FF, 十进制为 255 $hexa = 0xff; print "integer = $integer\n"; print "negative = $negative\n"; print "floating = $floating\n"; print "bigfloat = $bigfloat\n"; print "octal = $octal\n"; print "hexa = $hexa\n";
The above program, the output is:
integer = 200 negative = -300 floating = 200.34 bigfloat = -1.2e-23 octal = 255 hexa = 255
String-scalar
The following example demonstrates string scalar using different types of and attention to the difference between the single and double quotes:
#!/usr/bin/perl $var = "字符串标量 - 本教程!"; $quote = '我在单引号内 - $var'; $double = "我在双引号内 - $var"; $escape = "转义字符使用 -\tHello, World!"; print "var = $var\n"; print "quote = $quote\n"; print "double = $double\n"; print "escape = $escape\n";
The above program, the output is:
var = 字符串标量 - 本教程! quote = 我在单引号内 - $var double = 我在双引号内 - 字符串标量 - 本教程! escape = 转义字符使用 - Hello, World!
Scalar operations
The following example demonstrates a simple scalar operation:
#!/usr/bin/perl $str = "hello" . "world"; # 字符串连接 $num = 5 + 10; # 两数相加 $mul = 4 * 5; # 两数相乘 $mix = $str . $num; # 连接字符串和数字 print "str = $str\n"; print "num = $num\n"; print "mix = $mix\n";
The above program, the output is:
str = helloworld num = 15 mix = helloworld15
Multi-line strings
We can use single quotes to export multi-line string, as follows:
#!/usr/bin/perl $string = ' 本教程 —— 学的不仅是技术,更是梦想! '; print "$string\n";
The above program, the output is:
本教程 —— 学的不仅是技术,更是梦想!
You can also use "here" document syntax to output multiple lines:
#!/usr/bin/perl print <<EOF; 本教程 —— 学的不仅是技术,更是梦想! EOF
The above program, the output is:
本教程 —— 学的不仅是技术,更是梦想!
Special characters
Below we will demonstrate Perl application of special characters, such as __FILE__, __LINE__, and __PACKAGE__ represent the currently executing script file name, line number, the package name.
These special characters are separate tag can not be written in a string, for example:
#!/usr/bin/perl print "文件名 ". __FILE__ . "\n"; print "行号 " . __LINE__ ."\n"; print "包名 " . __PACKAGE__ ."\n"; # 无法解析 print "__FILE__ __LINE__ __PACKAGE__\n";
The above program, the output is:
文件名 test.pl 行号 4 包名 main __FILE__ __LINE__ __PACKAGE__
v String
V a beginning, followed by one or more integers separated by periods, and will be treated as a string literal.
When you want to directly declare its numeric value for each character, v- string provides a clearer method for constructing such a string, rather than "\ x {1} \ x {14} \ x { 12c} \ x {fa0} "this is not easy to understand, what I can see the following examples:
#!/usr/bin/perl $smile = v9786; $foo = v102.111.111; $martin = v77.97.114.116.105.110; print "smile = $smile\n"; print "foo = $foo\n"; print "martin = $martin\n";
The above program, the output is:
Wide character in print at test.pl line 7. smile = ☺ foo = foo martin = Martin