Any failure to use strict and warnings, or any use of no strict without a comment explaining why this is necessary.

Using 'no strict' without a comment is something you pay attention to, and I presume you flag it negatively? I disagree. I consider commenting the obvious as a sign of an immature or insecure coder. Commenting the obvious includes the classical:

    i++;   /* Increment i */
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but doesn't stop with:

    { no strict 'refs';
      *{$caller} = &{$something};
    }
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or

    my @list = do {no warnings; qw /foo #bar baz,/};
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Using backticks in void context. Or any other construct that returns a list, e.g., map

Nothing returns a list in void context. Lists are only returned in list context. And programmers who think that 'map' in void context creates a list internally are showing signs of not keeping up with modern Perl development. ;-).