One interesting possibility. Consider:

use strict;
use warnings;

sub MakeCounter {
    my $seed = 0;
    my $func = sub {return $seed++;};

    return $func;
}

my $counter1 = MakeCounter();
my $counter2 = MakeCounter();

for (1 .. 3) {
    $counter1->();

    $counter2->() for 1 .. 3;
}

printf "Count 1: %d, Count 2: %d\n", $counter1->(), $counter2->();
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Prints:

Count 1: 3, Count 2: 9
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