Why doesn't print output anything on each iteration of a loop when I use sleep?

Question

Today in my college a teacher asked me a question. He wrote this code on the paper and said \"What will be the output of this code?\"

use warnings;

for (1          


        

Answer 1

It's not clearing the buffer. If there is a newline at the end of the print statement it will do that for you automatically:

use warnings;

for (1 .. 20) {
    print ".\n";
    sleep 1;
}

If you don't want the newline (I don't imagine you do) you can use the special autoflush variable $|. Try setting it to 1 or incrementing it.

use warnings;

$|++;

for (1 .. 20) {
     print ".";
     sleep 1;
}