19.md

Perl 中的unless-elsif语句

原文： https://beginnersbook.com/2017/02/unless-elsif-else-statement-in-perl/

当我们需要检查多个条件时，使用unless-elsif-else语句。在这个声明中，我们只有一个unless和一个else，但我们可以有多个elsif。这是它的样子：

unless(condition_1){
   #These statements would execute if
   #condition_1 is false
   statement(s);
}
elsif(condition_2){
   #These statements would execute if
   #condition_1 & condition_2 are true
   statement(s);
}
elsif(condition_3){
   #These statements would execute if
   #condition_1 is true
   #condition_2 is false
   #condition_3 is true
   statement(s);
}
.
.
.
else{
   #if none of the condition is met
   #then these statements gets executed
   statement(s);
}

例

#!/usr/local/bin/perl

printf "Enter any number:";
$num = <STDIN>;
unless( $num == 100) {
   printf "Number is not 100\n";
}
elsif( $num==100) {
   printf "Number is 100\n";
}
else {
   printf "Entered number is not 100\n";
}

输出：

Enter any number:101
Number is not 100