#  set up data
my $tgt_left   = 1;
my $tgt_right  = 10;
my @data  = (0,0,0,0,0,1..10,100..150);

my $left  = 0;
$left++ while $data[$left] < $tgt_left;

my $right = $#data;
$right-- while $data[$right] > $tgt_right;

foreach my $i ($left..$right) {
  #  do stuff with @data
}