One answer to Check if an Array is a Member of an AoA is :

sub check_if_inst_occur_already {
  my ( $store, $inst_set ) = @_;
  foreach my $ins_already ( @{$store} ) {
    return 1 if is_equivalent($ins_already, $inst_set);
  }
  return 0;
}

sub is_equivalent{
  my ($aa, $bb) = @_;
  return 0 unless @$aa == @$bb;
  for( 0 .. @$aa-1){
    return 0 unless $aa->[$_] eq $bb->[$_];
  }
  return 1;
}
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