I need to do a reg expression on a word to find out if it has letters: "a" "b" "c"

I think to get one letter I do this: 
m(/a/g);

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Now how would i grab "a", "b" , "c"? 
m(/abc?/g)

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I am basically trying to count how many total I have of "a", "b" "c".

So if I had a word "fileCapaber"
My count would be 4 with the "C" two "a's" and one "b" All I need is the regular expression to fetch those letters out of a word. thanks.

In reply to Fetching 3 letters only by Anonymous Monk

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