The embedded my? Yes it's perfectly valid, although I quite agree that it looks odd, but the simple fact of the matter is that lexicals can be created pretty much anywhere in a statement.

It's (I think) what lets you do:

    if( my $foo = bar(@quux) ) {
        $foo exists here
    }
    # no foo here
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I'm certain it's what lets you say:

    (my $copy = $original) =~ s/foo/bar/;
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That is, the variable $copy doesn't fall out of scope outside the parentheses. Sometimes it makes for nicer code, sometimes bizarre. Be wary of trying this new toy out everywhere :)