in reply to John Guttag's book - 2nd exercise. My attempt in Perl.

Not 3 vars but any cli args: 
my $largest_odd;
for (@ARGV) {
    $largest_odd = $_ if $_ % 2 && $_ > $largest_odd;
}
print $largest_odd ? $largest_odd : 'nothing odd', $/;

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In Section Seekers of Perl Wisdom