After $try is modified, the next instruction is next which goes to the top of the while loop where $try is assigned a new value.    At no point is the value modified by ++$try or --$try used anywhere so you could just do:

    while ( $lo <= $hi ) {
        my $try = int( ( $lo + $hi ) / 2 );
        if ( $array[ $try ] lt $word ) {
            $lo = $try + 1; # without increment there will be
                            # a dead loop in the 4th case,
                            # see the note at the bottem
        }
        elsif ( $array[ $try ] gt $word ) {
            $hi = $try - 1;
        }
        else {
            return $try
        }
    }
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I misunderstood what you mean earlier. I hadn't noticed that $try was being modified in three places (rather than just at the top).

At no point is the value modified by ++$try or --$try used anywhere so you could just do:

That's not true. They're assigned to $lo and $hi respectively.

You probably meant to say that modifying $try here is superfluous. True, but irrelevant. Like you said, $try will get overwritten, so it doesn't matter if gets changed.

I would actually use +1 and -1, but keep in mind it's actually a teenie weenie bit faster to use pre-increment and pre-decrement.