sub bandpass {
    my( $aref, $loValue, $hiValue ) = @_;
    return if $loValue > $aref->[-1] or $hiValue < $aref->[0];
    my( $lo, $hi ) = ( 1, $#{ $aref } );
    $lo += $lo while                   $aref->[$lo]   <  $loValue;
    --$lo      while $lo           and $aref->[$lo-1] >= $loValue;
    $hi >>= 1  while                   $aref->[$hi]   >  $hiValue;
    ++$hi      while $hi < $#$aref and $aref->[$hi+1] <= $hiValue;
    return @{ $aref }[ $lo .. $hi ];
}
...
my $aref = $matches{ $fasta_id }{ $sitekey };
$sets{ $fasta_id }[ $setscounter ]{ $sitekey } = 
    [ bandpass( $aref, $lowerlimit, $upperlimit ) ];