perl 中的if-elsif-else语句

if(condition_1) {
   #if condition_1 is true execute this
   statement(s);
}
elsif(condition_2) {
   #execute this if condition_1 is not met and
   #condition_2 is met
   statement(s);
}
elsif(condition_3) {
   #execute this if condition_1 & condition_2 are
   #not met and condition_3 is met
   statement(s);
}
.
.
.
else {
   #if none of the condition is true
   #then these statements gets executed
   statement(s);
}

#!/usr/local/bin/perl

printf "Enter any integer between 1 & 99999:";
num = <STDIN>;
if(num <100 && num>=1) {
   printf "Its a two digit number\n";
}
elsif(num <1000 && num>=100) {
   printf "Its a three digit number\n";
}
elsif(num <10000 && num>=1000) {
   printf "Its a four digit number\n";
}
elsif(num <100000 && $num>=10000) {
   printf "Its a five digit number\n";
}
else {
   printf "Please enter number between 1 & 99999\n";
}

Enter any integer between 1 & 99999:8019
Its a four digit number