I agree with everyone else that List::Util::max() is the way to go here, but for your readability concerns, the layout of your code can have a huge influence on its readability. A slight restructuring can allow you to loose some of the parens, and make things clearer: 

use constant PADDING => 2;

my $col_width = PADDING + (
    sort { 
        $b <=> $a
    } map { 
        length
    } map {
        ref eq 'ARRAY' ? @$_ : $_   
    } %lists
)[ 0 ]; ## Longest key or value

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In reply to Re: I fear my code is unreadable by BrowserUk
in thread I fear my code is unreadable by Boldra

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