This uses a hash for the index rather than an array and push with a ternary.

johngg@aleatico:~$ perl -Mstrict -Mwarnings -MData::Dumper -E 'say q{}
+;
my @arr = ( q{a} .. q{m} );
my %idx = map { $_ => 1 } 2, 7 .. 9, 12;
my @slc;
my @inv;

push @{ $idx{ $_ } ? \ @slc : \ @inv }, $arr[ $_ ]
   for 0 .. $#arr;

print Data::Dumper->Dumpxs(
   [ \ @arr, \ @slc, \ @inv ],
   [ qw{ *arr *slc *inv } ] );'

@arr = (
         'a',
         'b',
         'c',
         'd',
         'e',
         'f',
         'g',
         'h',
         'i',
         'j',
         'k',
         'l',
         'm'
       );
@slc = (
         'c',
         'h',
         'i',
         'j',
         'm'
       );
@inv = (
      'a',
      'b',
      'd',
      'e',
      'f',
      'g',
      'k',
      'l'
    );

[download]

I hope this is of interest.

Update: Removed erroneous space in Dumpxs call which was mucking up the output.

Cheers,

JohnGG

In reply to Re: Inverse slices by johngg
in thread Inverse slices by Anonymous Monk

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