If all you're trying to accomplish is to reduce the effects of an eval in a tight loop, you could cache it.

{
 my %pwdrots;
 sub pwdrot {
    my $pwd = shift;
    my $degree = (@_ > 0) ? ((shift) % 94) : 47;

    if ($degree == 0) {
        return $pwd;
    }

    if (length($str) == 0) {
        return $pwd;
    }

    unless ($pwdrots{$degree})
    {
      my $rangstr = "\\" . sprintf("%03lo",$degree+33) . "-\\176\\041-
+\\" . sprintf("%03lo",$degree+32);
      $pwdrots{$degree} = eval "sub { $_[0] =~ tr[\041-\176][$rangstr]
+ }"
    }

    $pwdrots{$degree}->($pwd);

    return $pwd;
  }
}
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The idea is that you generate an anonymous sub which does the tr, once that is compiled once, you don't need to compile it again (for the same $degree).