In the spirit of TIMTOWTDI:

my @AoA;
for (0 .. $#list) {
    push @AoA, [] if $_ % $C == 0;
    push @{ $AoA[-1] }, $list[$_];
}
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or, without using indices:

my @AoA = [];

for (@list) {
    push @AoA, [] if $C == @{ $AoA[-1] };
    push @{ $AoA[-1] }, $_;
}
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