generating wordlist thru rule-based attack

[hetcat]

hi,

i am trying to build a word list as under :

mywords.rule

$abcd
$efgh
$ijklm

mynumbers.rule

$1111
$2222
$3333

... to generate wordslist as :
abcd1111
abcd2222
abcd3333
efgh1111
efgh2222
efgh3333
....
....

$ hashcat --stdout -r mywords.rule -r mynumbers.rule > wordlist

the command gives me an error : "no valid rules left" . please help me in to generate wordlist as above. can another .rule file with special character be added ? suggest the command specifically ...thanks