01_amb.p6

use MONKEY-SEE-NO-EVAL;

sub amb ($var, *@a) {
    my $r =                                  # DEBUG
    "[" ~ ("|| \{ $var = '$_' }" for @a) ~ "]";
     say "\n$r";                             # DEBUG
     $r                                      # DEBUG
}

sub joins ($word1, $word2) {
    my $r =                                  # DEBUG
    substr($word1,*-1,1) eq substr($word2,0,1);
    say "{$r ?? "✓" !! "✕"} $word1:$word2";  # DEBUG
    $r                                       # DEBUG
}

'' ~~ m/
    :my ($a, $b, $c, $d);
    
    <{ amb '$a', <the that a>           }>
    <{ amb '$b', <frog elephant thing>  }>
    <?{ joins $a, $b }>
    
    <{ amb '$c', <walked treaded grows> }>
    <?{ joins $b, $c }>
    { say "$a $b $c" }
    
    <{ amb '$d', <slowly quickly>       }>
    <?{ joins $c, $d }>
    
    { say "$a $b $c $d" }
    <!>
/;

03_output.txt

[|| { $a = 'the' } || { $a = 'that' } || { $a = 'a' }]

[|| { $b = 'frog' } || { $b = 'elephant' } || { $b = 'thing' }]
✕ the:frog
✓ the:elephant

[|| { $c = 'walked' } || { $c = 'treaded' } || { $c = 'grows' }]
✕ elephant:walked
✓ elephant:treaded
the elephant treaded

[|| { $d = 'slowly' } || { $d = 'quickly' }]
✕ treaded:slowly
✕ treaded:quickly