What I fail to see is a check that all words formed by adding tiles are kosher in both directions. It is the ability to do it in all 3 dimensions which separates the women from the men and their computter scripts now. I've added a bunch of (ugly) say statements in to proof the logic.

same is         ]
score values are arpeggio. 123312230 arpeggios
--------------------chosen: 0 56 arpeggios   score: 18
..a.......   0020000000
..j.......   0040000000
..i.......   0030000000
..v.......   0030000000
..a.......   0020000000
.arpeggios   0123312231
..........   0000000000
..........   0000000000
..........   0000000000
..........   0000000000
all is c e f o t y y   a e g i j o p r s v
moves: 10  tiles: c e f o t y y
in order is a?c?e?e?f?g?i?j?o?o?p?r?s?t?v?y?y?
array is 0 ..a.......
array is 11 ..j.......
...
array is 0 ..a..
array is 1 .a...
in order is a?c?e?e?f?g?i?j?o?o?p?r?s?t?v?y?y?
array is 11 .....a....
...
array is 33 .....p
array is 34 ....p.
inside if clause, changed is 7
same is MAZW K
score values are ....p. 000030 cotype
--------------------chosen: 1 34 cotype   score: 8
..a.......   0020000000
..jc......   0041000000
..io......   0031000000
..vt......   0031000000
..ay......   0021000000
.arpeggios   0123312231
...e......   0001000000
..........   0000000000
..........   0000000000
..........   0000000000
[download]

What we see here are non-words forming in the axis opposite to those in which the tiles are laid.

Current source. I included johngg's alternate way to form tile bag, if only because I like to run everyone's source when they post on one of my threads. I'm not insisting that it's The Right way to do it. I can always use practice with quote-like operators.

#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11108138
use warnings; 
use feature 'say';

use Path::Tiny;
use List::Util qw( shuffle uniq first );
$SIG{__WARN__} = sub { die @_ };

my $n = 10;            # configuration  board will be  $n by $n
my $maxtiles = 7;
my $dict = 'c:\users\tblaz\documents\html_template_data\dict\enable1.t
+xt';

my $n1 = $n + 1;
my $board = ('.' x $n . "\n") x $n; #board represented as string
my $heights = $board =~ tr/./0/r;
my @dictwords;
my $filename = "words.11108138.$n"; # for caching
if( -f $filename )
  {
  @dictwords = split /\n/, path($filename)->slurp;
  }
else
  {
  print "caching words of length $n\n";
  @dictwords = sort { length $b <=> length $a }
    grep /^[a-z]{2,$n}$/,
    split /\n/, path($dict)->slurp;
  path($filename)->spew(join "\n", @dictwords, '');
  }
  


my @drawpile = shuffle +  do {
   my @chars   = ( q{a} .. q{z} );
   my @counts  = (
      9, 2, 2, 4, 12, 2, 4, 2, 9, 1, 1, 4, 2,
      6, 8, 2, 1, 6, 4, 6, 4, 2, 2, 1, 2, 1 );
   map { ( $chars[ $_ ] ) x $counts[ $_ ] } 0 .. 25;
   };
my @tiles = sort splice @drawpile, 0, $maxtiles;
print "tiles: @tiles\n";
my $pat = join '', map "$_?", @tiles;

my $word = first
  { /^[@tiles]+$/ and (join '', sort split //) =~ /^$pat$/ } @dictword
+s;
$word or die "no starting word can be found\n";
say "word is $word";
substr $board, $n1 * ($n >> 1) + ($n - length($word) >> 1),
  length $word, $word;
substr $heights, $n1 * ($n >> 1) + ($n - length($word) >> 1),
  length $word, 1 x length $word;
my @chosen = $word;
my $changed = 1;
my $moves = 0;
my $totalscore = 2 * length $word;
printboard();

say "execution point 1; enter to continue";
my $prompt = <STDIN>;

while( @tiles )
  {
  $heights =~ tr/5// == $n ** 2 and last; # ??
  my @best; # [ flip, pos, pat, old, highs, word ]


  my @all = (@tiles, ' ', sort +uniq $board =~ /\w/g);
  say "all is @all";
  $moves++;
  print "moves: $moves  tiles: @tiles\n";
  my @subdict = grep /^[@all]+$/, @dictwords;
  #say "subdict is @subdict";
  for my $flip ( 0, 1 )
    {
    my $inorder = join '', map "$_?", sort "@all" =~ /\w/g;
    say "in order is $inorder";
    my $orderpat = qr/^$inorder$/;

    my @pat;
    $board =~ /(?<!\w).{2,}(?!\w)(?{ push @pat, [ $-[0], $& ] })(*FAIL
+)/;
    @pat = map expand($_), @pat;
    @pat = sort { length $b->[1] <=> length $a->[1] } @pat;

    for ( @pat )
      {
      my ($pos, $pat) = @$_;
      my @array = @$_;
      say "array is @array";
      my $old = substr $board, $pos, length $pat;
      my $highs = substr $heights, $pos, length $pat;
      my @under = $old =~ /\w/g;
      my $underpat = qr/[^@under@tiles]/;
      #say "under pat is $underpat";
      my $w = first {
        length $pat == length $_
        && !/$underpat/
        && /^$pat$/
        && ( /s$/ ? $pat ne s/s$/./r : 1 )
        && matchrule( $old, $highs, $_ )
        } @subdict;
      $w and $best[ length $w ] //=
        [ $flip, $pos, $pat, $old, $highs, $w ], last;
      }
    transpose();
    }
  if( $changed = @best )
    {
    say "inside if clause, changed is $changed";
    
    my ($flip, $pos, $pat, $old, $highs, $word) = @{ $best[-1] };
    $flip and transpose();
    my $usedtiles = '';
    $usedtiles = $word;
    my $same = $word ^ substr $board, $pos, length $word;
    say "same is $same";
    my $tmppos = $pos;
    for ( split //, $same )
      {
      if( $_ ne "\0" )
        {
        substr( $heights, $tmppos, 1 ) =~ tr/0-4/1-5/; # new tile, add
+ 1
        }
      else
        {
        $usedtiles =~ s/$_// for substr $board, $tmppos, 1;
        }
      $tmppos++;
      }
    substr $board, $pos, length $word, $word;
    $totalscore += my $score = score( $old, $highs, $word );
    print '-' x 20, "chosen: $flip $pos $word   score: $score\n";
    push @chosen, $word;
    $flip and transpose();
    my $tiles = join '', @tiles;
    $tiles =~ s/$_// for split //, $usedtiles;
    @tiles = split //, $tiles;
    }
  else
    { 
    splice @tiles, rand @tiles, 1; # discard random tile
    }
  @tiles = sort @tiles, splice @drawpile, 0, $maxtiles - @tiles;
  $changed and printboard();
  }
print "\nchosen words: @chosen\ntotalscore: $totalscore\n";

sub score
  {
  my ($old, $high, $word) = @_;
  say "score values are $old $high $word";
  my $score = ($old ^ $word) =~ tr/\0//c == $maxtiles ? 20 : 0;
  $score += chop($high) + (chop($old) ne $_) for reverse split //, $wo
+rd;
  $score == length $word and $score *= 2; # no stacked letters
  return $score;
  }

sub printboard
  {
  my $bd = $board =~ tr/\n/-/r;
  $bd =~ s/-/   $_/ for $heights =~ /.*\n/g;
  print $bd;
  }

sub matchrule
  {
  my ($old, $highs, $word) = @_;
  #say "in match rule";
  $old eq $word and return 0; #old word cannot be identical
  my $newmask = ($old ^ $word) =~ tr/\0/\xff/cr;
  #say "new mask is $newmask";
  ($newmask & $highs) =~ tr/5// and return 0;
  my $tiles = "@tiles";
  $tiles =~ s/$_// or return 0 for ($newmask & $word) =~ /\w/g;
  return 1;
  }

sub transpose # both board and heights arrays
  {
  local $_ = $board;
  $board = '';
  $board .= "\n" while s/^./ $board .= $& ; '' /gem;
  $_ = $heights;
  $heights = '';
  $heights .= "\n" while s/^./ $heights .= $& ; '' /gem;
  }

sub expand # change patterns with several letters to several single le
+tter pats
  {
  my @ans;
  my ($pos, $pat) = @{ shift() };
  push @ans, [ $pos, $` =~ tr//./cr . $& . $' =~ tr//./cr ]
    while $pat =~ /\w/g;
  return @ans;
  }
__END__
[download]

Actually, I'll just hang on to my questions until I can frame them better. I wanted the prolific tybalt89 to see what remains yet to achieve in the core functionality.