@$aref = @$aref[++$mid..$#$aref];
...
@$aref = @$aref[0..--$mid];

##</code><code>##

sub binary_search {
	my ($aref, $find) = @_;
	my  $mid;

	$mid = int $#$aref / 2;

	return 0 if $find == $aref->[$mid];
	return 1 if !$#$aref;

	if ($find > $aref->[$mid]) {
		binary_search([ @$aref[++$mid..$#$aref] ], $find);
	}
	else {
		binary_search([ @$aref[0..--$mid] ], $find);
	}
}

##</code><code>##

sub binary_search {
	my ($aref, $find) = @_;
	my  $mid = int $#$aref / 2;

	return 0 unless $#$aref;
	return 1 if $find == $aref->[$mid];

	binary_search(
		$find < $aref->[$mid]
		? [ @$aref[     0 .. --$mid ] ]
		: [ @$aref[++$mid .. $#$aref] ]
		, $find
	);
}