You can use the select() function to do short sleeps. If your system doesn't support a four-argument select(), you can use the Time::HiRes module. For the select function, the last argument reflects the time to sleep. This comes right out of O'Reilly's Perl Cookbook:

while (<>) {
    select(undef, undef, undef, 0.25);
    print;
}
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Using Time::HiRes, we'd write it as:

use Time::HiRes qw(sleep);
while (<>) {
    sleep(0.25);
    print;
}
[download]

Funny thing is that I used nearly the same method of making a spinner a while back...and I had the exact same question about slowing it down. Hope this helps!