use v5.24;
use strict;
use warnings;

# bad output
{
    print "A: sleeping for 5s ...";
    sleep 5;
    print "woke up\n";
}

# cryptic solution
{
    print "B: sleeping for 5s ...";
    local $| = 1;
    sleep 5;
    print "woke up\n";
}

# just to show that $| was localised
{
    print "C: sleeping for 5s ...";
    sleep 5;
    print "woke up\n";
}

# still cryptic, but nicer solution
{
    print "D: sleeping for 5s ...";
    select()->flush();
    sleep 5;
    print "woke up\n";
}