Blanks are specified by putting numbers in double curly braces:

{{0}} - noun
{{1}} - proper noun
{{2}} - adjective
{{3}} - adverb

Verbs:
{{4}} - simple tense (root)
{{5}} - continuous tense (root -ing)
{{6}} - perfect tense (root -ed)

Words can be cached and later recalled using this syntax: {{0, 0}}
The second number is an identifier. Identifiers are not shared between parts of speech, so {{0, 0}} and {{1, 0}} do not recall the same word.

Words can be pluralized with this syntax: {{0 pl}}

Words can have suffixes added with this syntax: {{4 -ed}}
"ed" can be replaced with any suffix.

pl and -suffix can't be stacked with each other, and if both are present, pl is preferred. pl and -suffix both stack with caches, and only the root word is cached.

'Twas {{2, 0}}, and the {{2, 1}} {{0, 0}} Did {{4, 0}} and {{4, 1}} in the {{0, 1}}: All {{2, 2}} were the {{0, 2}}, And the {{2, 3}} {{0, 3}} {{2, 4}}. "Beware the {{1, 0}}, my son! The jaws that bite, the claws that catch! Beware the {{1}}, and shun The {{2}} {{1}}!" He took his {{2, 5}} sword in hand: Long time the {{2}} foe he sought-- So he rested by the {{1}} tree, And stood awhile in thought. And, as in {{2}} thought he stood, The {{1, 0}}, with eyes of flame, Came {{5}} though the {{2}} wood, And {{6}} as it came! One, two! One, two! And through and through The {{2, 5}} blade went snicker-snack! He left it dead, and with its head He went {{5}} back. "And hast thou slain the {{1, 0}}? Come to my arms, my {{2}} boy! O {{2}} day! Callooh! Callay!" He {{6}} in his joy. 'Twas {{2, 0}}, and the {{2, 1}} {{0, 0}} Did {{4, 0}} and {{4, 1}} in the {{0, 1}}: All {{2, 2}} were the {{0, 2}}, And the {{2, 3}} {{0, 3}} {{2, 4}}.