Here is a time-based version using perldoc -f sleep

use warnings;
use strict;

my @cmd = 1 .. 200;
my $i = 0;
for (@cmd) {
    print "$_\n";
    $i++;
    sleep 2 if $i % 20 == 0;
}
[download]

See also:

• perlintro
• perlop