binary search in perl, using the goto form of tail-recursion elimination

bsearch.pl

#!/usr/bin/perl
use Test::Simple tests=>4;

sub bsearch {
        my ($aref, $item, $lo, $hi)  = @_;
        return -1 if $lo > $hi;
        my $mid = ($hi + $lo) >> 1;
        return $mid if ($aref->[$mid] == $item);
        if ($item > $aref->[$mid]) {
                @_ = ($aref, $item, $mid+1, $hi);
                goto &bsearch;
        }else{
                @_ = ($aref, $item, $lo, $mid - 1);
                goto &bsearch;
        }
}

my @a = (-1,0,1,3,5,6,7,9);

my $len = @a - 1;

ok(-1 == bsearch(\@a, 4, 0, $len));
ok(3  == bsearch(\@a, 3, 0, $len));
ok(2  == bsearch(\@a, 1, 0, $len));
ok(7  == bsearch(\@a, 9, 0, $len));