1.@_含义
1)是perl中默认的数组变量
比如说你想移除数组中的一个元素赋值给一个变value方法1:你可以定义某个数组如@abcdmyvalue=shift @abcd;
方法2:你没有定义任何数组 my $value=shift @_; 和上例等效 这里perl会隐式的选择@_
2)是sub子函数中的默认参数列表.
例如: sub funct($$) { ($param1, $param2) = @_; #Statement }
再例如,有下面一段代码: my max_number = &max(1,2); print "1 and 2 ,the max number ismax_number\n"; sub max{ my (num1,num2) = @_[0,1]; ## 取出参数列表中的元素。 ........此处省略求max运算 }
在子函数中直接shift; 就可以从@_的前端弹出一个元素.
shift; 等于 shift @_;
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@_ is the list of incoming parameters to a sub. So if you write a sub, you refer to the first parameter in it as $_[0], the second parameter as $_[1] and so on. And you can refer to $#_ as the index number of the last parameter: sub demo { print "Called with ",#_+1," params\n"; print "First param was_[0]\n";
Note that the English module adds in the ability to refer to the special variables by other longer, but easier to remember, names such as @ARG for @_ and PIDfor$. But use English; can have a detrimental performance effect if you're matching regular expressions against long incoming strings
2.$_含义
1)为默认列表变量。在一个命令没有任何参数的时候,表示它从默认变量里读取。例如:print;等于print_; 2)默认模式匹配空间(pattern matching space) s/.../.../; 等于 $_ =~ s/.../.../;
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Then any regular expression matches, chops (and lcs and many more) without a parameter, and even prints assume you want to work on .Thus:while(line = <FH>) { if (line= /Perl/)printFHO$line;printucline; }
Shortens to: while (<FH>) { /Perl/ and print FHO ; print uc; } 3.1,2,...等含义
以数字为名的变量保存的是上一次匹配操作(/pattern/)中,第n个小括号中的原符号所匹配内容。 1就是第一对小括号中的原符号所对应的匹配内容。2就是第二对小括号中的原符号所对应的匹配内容。
内插功能: str="aaa4zzz7bbb";str =~ /(\d)z{3}(\d)/; print "1\t2n";
输出结果是:4 7
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