how to count number of occurances in perl regular expression?

[avinash]

if i want to find whether a pattern is strictly a permutation of previously known text or not . what regular expression i need to check with?
for example if known text is 'genome'

i can test that a word is made up of the same letters in 'genome' with regular expression but i cant test the number of occurance i am also writing some test cases based on this exanple
all permutations of 'genome'
'eenomg' should match
'gonmee' should match
'egonme' should match
so on...