Thank you choroba, I am a bit confused as to what you do in your sub-routine...
Could you maybe explain this a bit?

sub p
{
  my($w,$v)=@_;
  for my $e(1..$#chars_all)
  {
    if($w**2+$v**2<($e*20/$#chars_all)**2)
    {return $chars_all[$e]} 
  }' '
}
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Particularly, I can't understand the  }' ' part that you have...
Thank you very much!