in reply to do something no more than 3 times a second

Well, you cannot sleep for half a second using the standard sleep function; you'd need the sleep from Time::HiRes. I would only sleep if there's an actual need to sleep. Perhaps something like: 
sub do_request {
    use Time::HiRes qw[sleep time];
    use 5.010;
    state $sleep = [0, 0, 0];
    my $url = shift;
    while ($$sleep[0] + 1 > time) {
        # Loop, as sleep() may get interrupted.
        sleep time - $$sleep[0] + 1;
    }
    $sleep = [@$sleep [1 .. $#$sleep], time];
    ... fetch from server ...
}

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Re^2: do something no more than 3 times a second
by BrimBorium (Friar) on Nov 26, 2010 at 20:22 UTC

    you could use select as described in perlfunc

    You can effect a sleep of 250 milliseconds this way:
   select(undef, undef, undef, 0.25);

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[d/l]
      Sure, but select() isn't the standard sleep either. And you still need to figure out what the fourth argument should be - select() isn't going to tell you that.
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