Alternatively, you can just use splice with a negative offset to remove elements from the end

#!perl
use strict;
use warnings;

while (<DATA>){
  chomp;
  my $aref = [ split /\s+/,$_ ];
  print join ' ', 'Original Array:', @$aref,"\n";

  my $start; my @copy=(); my $i=0;
  for (@$aref){
    push @copy,$_;
    if ($_ == 6){
      $start = $i unless defined $start;
    } elsif (defined $start && $_ == 7){
      splice @copy, $start-$i-1;
      $start = undef;
    }
    ++$i;
  }
  print join ' ','Results:',@copy,"\n"; 
}

__DATA__
1 6 2 2 7 1 6 99 99 7
1 2 2
1 1 6 7 2
1 6 2 2 7 1 6 99 99 7
2 7 6 2 6 7 2 7
1 6 7 7
2 7 6 2 6 2 7
6 7 1 6 7 7
6 8 1 6 7
[download]

There's another way to do it: use decreasing indices and iterate from the end to the beginning. This keeps the arrays aligned after splice.