Borrowing from I0, I offer this alternative:

return map {
    if(  s/^2//  ) {
        $_;
    } elsif(  /^([01])(\d\d\d)(.*)\Q$;\E(.*)$/  ) {
        $3 . substr(300-$2,-2) . $4 . "_" . ($str1,$str2)[$1]
    }
} sort map {
    if(  ! /(.*)(\d\d)(.*)_(?:\Q$string1\E|(\Q$string2\E))$/  ){
        2.$_;
    }else{
        (0+defined($4)) . (200-$2) . $1 . $; . $3;
    }
} @strs;
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which may be the fastest yet once you get enough elements to sort (and you have to set $; to something that won't be in your strings).

        - tye (but my friends call me "Tye")