As others have already pointed out, you need to explicitly call exit in the portion that will be executed by the child processes. In other words, try something a bit more like this:

#!/usr/bin/env perl 

use strict;
use warnings;

my @a = (1,2,3);

for my $i (@a) {

    my $pid = fork();

    if ( $pid == 0 ) {
        print "$i -> i am a forked child\n";
        exit;
    } else {
        print "$i -> forking $pid\n";
    }
}

while((wait()) > 0) {};
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See perlfork and perlipc for more examples.

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)