Funny, I've always interpreted that particular advice in the context of nested parens. The last paren that has a match on the current line should get a space, but I think it only applies with nested parens. I.e.:

#do this:
if (($a+b) eq ($c-$d) ) { }

#instead of:
if (($a+b) eq ($c-d)) { }

#but I do:
if ( ($a+b) eq ($c-$d) ) { }
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It never even occured to me that it could mean something different.