To all those, including myself, who are using, or had used, two lists (a..z , A..Z): Why not just convert the string to either upper or lower case before working on it so that only 26-element list, instead of 52, would be needed?

In my case ... i didn't even think of it until i was working on the Rexx solution. To repent, below is perl translation....

sub has_alpha
{ my ($string) = @_;

  return unless length $string;

  $string = lc $string;
  my ($start , $stop) = qw/a z/;

  while ($start le $stop)
  { index($string , $start++) != -1 and return 1;
  }
  return;
}
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