Binary Search

#!/usr/bin/perl
#
#bsearch - search for a word in a list of alphabetically ordered words
#Usage: bsearch word filename

$word = shift;
@array = <>;

($word, @array) = map { lc } ($word, @array);
@array = map { s/(\n|\r)+// && $_ } @array;
$index = binary_search(\@array, $word);

if (defined($index)) {
    print "{$word} occurs at position $index.\n";
} else {
    print "{$word} doesn't occur.\n";
}

# $index = binary_search( \@array, $word )
#  @array is a list of lowercase strings in alphabetical order.
#  $word is the target word that might be in the list.
#  binary_search() returns the array index such that $array[$index]
#  is $word.

sub binary_search {
    my ($array, $word) = @_;
    my ($low, $high) = (0, @$array - 1);

    while ( $low <= $high) {
    my $try = int( ($low + $high)/2 );
    print "DEBUG:$try {$array->[$try]}\n";
    $low = $try + 1, next if $array->[$try] lt $word;
    $high = $try - 1, next if $array->[$try] gt $word;
    return $try;
    }
    return;
}