$|=1; #autoflush

sub spin {
my @spinners = qw{/ - \ |};
my $index = $_[0];
print $spinners[$index]."\033[1D"; # man console_codes, ECMA-48 CSI sequences, "CUB"
return $index == 3 ? 0 : $index++;
}

my $j=0;
for (something) {
 do_something;
 $j=&spin($j);
}