use strict;
use warnings;

my @AoA = (
    [12,13,14,15,16,17,18,19],
    [20,21,22,23],
);

my @a = (14,15,16,17,18,19);

my @index = grep {
    my $i = $_;
    my %seen = map {$_ => 1} @{$AoA[$i]};
    ! grep {!$seen{$_}} @a;
} keys @AoA;

print "\@a is within index $_\n" for @index;
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