I agree that those cases don't make much sense. But with long and complex condition statement, I occassionally break it in some way to help myself understand it, for example:

if (($a1 == $a2) && 
    ($a3 == $a4) && 
    (($a5 == $a6) || ($a7 == $a8))
   ) 
{
}
[download]

This way of breaking makes it clear (at least to me) that those lines are at the same level.

FWIW, I prefer to treat all paired delimiters the same (ie parens, brackets and braces all follow the same rules). When I break a single expression over multiple lines, I put the “connecting” ops at the front of the new line, instead of hanging them off them end of the previous one. And I use whichever set of boolean ops require the fewest parens (usually, the low-precedence ones) – in fact I always aim for the fewest paired delimiters possible, and only add optional ones deliberately when the result is too uniform and devoid of visual hooks. In this style, your example would be:

if (
    $a1 == $a2
    and $a3 == $a4
    and ( $a5 == $a6 or $a7 == $a8 )
) {
    # ...
}
[download]

Makeshifts last the longest.

Of course, the spelled keywords 'and' and 'or' help de-parentheficate this sort of thing slightly:

if ( $a1 == $a2 and
     $a3 == $a4 and
     ($a5 == $a6 or $a7 == $a8) )
{
}
[download]

For readability, I also pull some tests into literate (readable, self-documenting) boolean names: my $nouns_match = ( $a3 == $a4 ). Then I can just refer to $nouns_match in the complicated conditional.

--
[ e d @ h a l l e y . c c ]

Ahh. For what its worth. When it said matching I though the expresion part of an if block. Although looking at those, the wording isn't very clear.