use strict;
use warnings;
use Data::Dumper;

my @skip_idx = (6,13,42,66,69);
my @array = ();
my @invarray = ();

my $idx = -1;
foreach my $str ('aa'..'zz') {
  ++$idx;
  if (grep { /^$idx$/ } @skip_idx) { # could use List::Util::any here
    push @invarray, $str;
    print "skipped '$str' (index of $idx)\n";
  }
  push @array, $str;
}

print Data::Dumper::Dumper(\@invarray);