The binary search approaches in 11134164 and 11134184 are probably best. However, if the range indices are usually near the ends of the arrays then it would also be worth looking at a simple linear search. This is particularly so if they are, on average, in the first and last ten items as then you have 10+10=20 iterations without much overhead.

Something like this (untested) code might work:

#  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
}
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Benchmarking would be needed to confirm or otherwise.