“Sometimes, it requires executing one or more statements based on a particular condition. This problem can be solved by using the “if” statement. It is a very useful statement for any programming language. The ways of using different types of “if” statements in the PERL script have ...
if (Expression) {Code Segment} else {Code Segment} if (Expression) {Code Segment} elsif (Expression) {Code Segment} else {Code Segment} # elsif 就是 else if # 如果指令(statement)只有一项,我们可以使用倒装句法,看起来比较简洁。 statement if (Expression); # unless 就是if not statement unless...
if (Expression) {Code Segment}elsif(Expression) {Code Segment} else {Code Segment} # elsif 就是 else if # 如果指令(statement)只有一項,我們可以使用倒裝句法,看起來比較簡潔。 statementif(Expression); # unless 就是if not statementunless(Expression); 例: print "HELLO!\n" if ($name eq "frien...
if (Expression) {Code Segment} else {Code Segment} if (Expression) {Code Segment} elsif (Expression) {Code Segment} else {Code Segment} # elsif 就是 else if # 如果指令(statement)只有一項,我們可以使用倒裝句法,看起來比較簡潔。 statement if (Expression); # unless 就是if not statement unless...
举个例子，比如我们要匹配Http状态的话，没有模式匹配的，使用if/else的话，会写成下面这样：
What is this Perl statement all about?"Hello World"is a simple double-quoted string."World"is the regular expression and the"//"enclosing"/World/"tells Perl to search a string for a match. The operator"=~"associates the string with the regexp match and produces a true value if the reg...
First, an array slice doesn’t return an empty list, so you can’t use that as a condition in the while as in the previous examples. Since it fills in the missing elements with undef, outputting the values possibly comes with warnings. Even if you want to accept those annoyances, you...
Returns true if it succeeded, false otherwise. NAME should be a packed address of the appropriate type for the socket. See the examples in "Sockets: Client/Server Communication" in perlipc. continue BLOCK continue "continue" is actually a flow control statement rather than a function. If ...
Check current element matches the given element using the if conditional statement. prints a string to the console. Here is an example @numbers= (1, 2, 3,4,5,6);my$searchElement=1;for(@numbers) {if($_eq$searchElement) {print"exists";last;}} ...
if 语句 当您需要检查语句的返回值时, if statement是显而易见的选择; 例如 - if(open(DATA, $file)) { ... } else { die "Error: Couldn't open the file - $!"; } 123456 这里变量$! 返回实际的错误消息。 或者,我们可以在有意义的情况下将陈述减少到一行; 例如 - ...