G'day sbrothy,

I suggest you take a look at Regexp::Debugger. That will allow you to step through the matching process and see exactly what is going on.

A note on usage. The tr/// operator does not have [...] character classes like regexes (as might be used in s///), but only ranges, e.g., a-z, so the \[ [ ] sequences in the tr/\[A-Z]/[a-z]/ expression in the OP represent literal [ ] characters (see tr/// in Quote-Like Operators in perlop).

So '[' is being translated to '[' and ']' to ']'. This does no harm (indeed, the tr/// compiler may optimize this away), but suggests a misunderstanding of tr///.

And since the tr/// is just translating upper case to lower, a simple
    $_ = lc;
statement might be clearer, hence better (see lc).

Update: I see now that Marshall has already made this point at the end of this post.

I'm sure there's a better Perl scrabble cheater already in existence, but I enjoyed the exercise. The "requirement" I sought to satisfy is that given a word already on the scrabble board and a tray of letters one can use to augment the word, return a list of all words from a standard dictionary that can be formed from the given word using only one or more letters from the tray added to the beginning and/or end of the given word.

This code is minimally tested, but looks good to me. It also seems a good candidate for encapsulation in a module with a thorough test file. There are also a few enhancements one can imagine, e.g., listing the candidate words found along with their scrabble scores and in order sorted by score/alpha. I think this code will work under Perl version 5.8.9, but I haven't tested it with this version. The dictionary I used for testing is not an "official" scrabble dictionary, but a general dictionary I had on hand.

scrabble_cheater_3.pl:

Win8 Strawberry 5.30.3.1 (64)  Tue 09/07/2021  6:24:31
C:\@Work\Perl\monks\Marshall
>perl scrabble_cheater_3.pl
given: 'led'
tray:  'ooidgkle'
 deLED
doiLED
 doLED
dolLED
gelLED
gilLED
  gLED
  gLEDe
 idLED
kilLED
   LEDe
   LEDge
   LEDged
   LEDol
 ogLED
 oiLED

Win8 Strawberry 5.30.3.1 (64)  Tue 09/07/2021  7:22:34
C:\@Work\Perl\monks\Marshall
>perl scrabble_cheater_3.pl  -g no  -t wk
given: 'no'
tray:  'wk'
kNOw
 NOw
[download]

Sorry I don't see your problem, could you please describe it better and provide a SSCCE ?

> Will you humor me one last time?

We are happy to help, as long as you don't make it unnecessary difficult for us. :)

Certainly. I realize it's probably tldr. Let me give it another go before you waste your time...

OK, I shortened it, hope this is more acceptable. In the process I discovered, as I suspected, that it has something to do with the regex order, but exactly what is still pretty opaque to me.

#!/usr/bin/perl

my @words = ('aa', 'as', 'es', 'is', 'os', 'sh', 'si', 'so');
print "WORDS: @words\n";

print "----------------------------\n";

my $regex = ".?a?";
print "Matches for regex pattern : $regex\n\n";

foreach (@words) {
    if(join('', sort split //, $_) =~ /^$regex$/) {
        print "$_\n";
    }
}

print "----------------------------\n";

my $regex = "a?.?";
print "Matches for regex pattern : $regex\n\n";

foreach (@words) {
    if(join('', sort split //, $_) =~ /^$regex$/) {
        print "$_\n";
    }
}

print "----------------------------\n";

$regex = "s?.?";
print "Matches for regex pattern : $regex\n\n";

foreach (@words) {
    if(join('', sort split //, $_) =~ /^$regex$/) {
        print "$_\n";
    }
}


print "----------------------------\n";

$regex = ".?s?";
print "Matches for regex pattern : $regex\n\n";


foreach (@words) {
    if(join('', sort split //, $_) =~ /^$regex$/) {
        print "$_\n";
    }
}


print "----------------------------\n";
[download]

OUTPUT

WORDS: aa as es is os sh si so
----------------------------
Matches for regex pattern : .?a?

aa
----------------------------
Matches for regex pattern : a?.?

aa
as
----------------------------
Matches for regex pattern : s?.?

----------------------------
Matches for regex pattern : .?s?

as
es
is
os
sh
si
so
----------------------------
[download]

Regards.

BTW: If you are going to do matching against a word list after the words in the list have had their letters sorted into alpha order and if you will do many matches against the same word list, it will be (possibly much) more efficient to first build a hash of all sorted versus native words.

Win8 Strawberry 5.8.9.5 (32)  Mon 09/06/2021  1:53:18
C:\@Work\Perl\monks
>perl -Mstrict -Mwarnings
use Data::Dump qw(dd);  # for debug

my @words = (  # added a few extra 'words'
'', 'x', 'a', 's', 'aa', 'as', 'es', 'is', 'os', 'sh', 'si', 'so'
);
dd '@words:', \@words;  # for debug

# map words to sorted words.
my %sorted = map { $_ => join('', sort split //) } @words;
dd 'sorted words hash:', \%sorted;  # for debug

print "----------------------------\n";

for my $regex (qw(.?a?  a?.?  s?.?  .?s?)) {

    my $rx_full = qr{ ^ $regex $ }x;      # faster if used often
  # my $rx_full = qr{ \A $regex \z }xms;  # i prefer \A \z \Z and /xms
+ tail

    print "Matches for FULL regex pattern: $rx_full \n";

    for my $word (@words) {
        print "'$sorted{$word}' -> '$word'  " if $sorted{$word} =~ $rx
+_full;
        }

    print "\n----------------------------\n";

    }

^Z
(
  "\@words:",
  ["", "x", "a", "s", "aa", "as", "es", "is", "os", "sh", "si", "so"],
)
(
  "sorted words hash:",
  {
    ""   => "",
    "a"  => "a",
    "aa" => "aa",
    "as" => "as",
    "es" => "es",
    "is" => "is",
    "os" => "os",
    "s"  => "s",
    "sh" => "hs",
    "si" => "is",
    "so" => "os",
    "x"  => "x",
  },
)
----------------------------
Matches for FULL regex pattern: (?x-ism: ^ .?a? $ )
'' -> ''  'x' -> 'x'  'a' -> 'a'  's' -> 's'  'aa' -> 'aa'
----------------------------
Matches for FULL regex pattern: (?x-ism: ^ a?.? $ )
'' -> ''  'x' -> 'x'  'a' -> 'a'  's' -> 's'  'aa' -> 'aa'  'as' -> 'a
+s'
----------------------------
Matches for FULL regex pattern: (?x-ism: ^ s?.? $ )
'' -> ''  'x' -> 'x'  'a' -> 'a'  's' -> 's'
----------------------------
Matches for FULL regex pattern: (?x-ism: ^ .?s? $ )
'' -> ''  'x' -> 'x'  'a' -> 'a'  's' -> 's'  'as' -> 'as'  'es' -> 'e
+s'  'is' -> 'is'  'os' -> 'os'  'hs' -> 'sh'  'is' -> 'si'  'os' -> '
+so'
----------------------------
[download]

«…cheat at Scrabble…»

See Games::Literati. I don’t know if it’s good but it seems like it is maintained. Best regards, Karl

I did come close to your output for "s." but not exactly.
My output for "a." is wildly off from what you show.

I downloaded your DB file to a local file to make my testing faster.
I don't think that makes any difference.

I would like more text to describe what you want to have happen.

#!/usr/bin/perl

use strict;
use warnings;

my @words;
open my $fh, '<', 'EuroScrabbleWordList.txt' or die "can't open word l
+ist $!";

foreach (<$fh>) 
{
    tr/\r\n//d;     
    tr/A-Z/a-z/;            
    next if /\s/; # dirty way of removing comments 
    push @words, $_;
}

close $fh;


############################################
my $tiles = 'a.';
# print all words with 2 letters that contain "a"
print "\nMATCHES FOR: $tiles\n";
my @m = find_matches($tiles);
print "\n@m\n";

$tiles = 's.';
# print all words with 2 letters that contain "s"
print "\nMATCHES FOR: $tiles\n";
@m = find_matches($tiles);
print "\n@m\n";

$tiles = 'a.a';
#print all words with letters that contain 2 a's
print "\nMATCHES FOR: $tiles\n";
@m = find_matches($tiles);
print "\n@m\n";


############################################
sub find_matches 
{
    my $pattern = shift;
    my $max_chars = length $pattern;
    
    my @matches;
    
    $pattern =~ s/\W+//g; #delete the dots
    my $raw_letters = $pattern;
         
    my $regex = "";
    $regex .= "[$raw_letters].?" for (1..length $raw_letters);
    print "$regex\n";
    
    foreach my $word (@words)
    {
       next if (length ($word) > $max_chars);
       
       push (@matches, $word) if $word =~ /$regex/;
    }
   
    return @matches;
}

__END__
MATCHES FOR: a.
[a].?

aa ab ad ae ag ah ai al am an ar as at aw ax ay ba da ea fa ha ja ka l
+a ma na pa ta ya za

MATCHES FOR: s.
[s].?

as es is os sh si so st us

MATCHES FOR: a.a
[aa].?[aa].?

aa aah aal aas aba aga aha aia aka ala ama ana aua ava awa baa caa faa
+ maa
[download]

In terms of algorithms, let's start with something simple:
for "s.":

You say: as es is os sh si so
I say:   as es is os sh si so st us
[download]