Re: REgular expression to check the string that allows "a","b" and "c" to occur only once in any order.

m/
    (?=^[^a]*a[^a]*$) ## One a and no other a's
    (?=^[^b]*b[^b]*$) ## One b and no other b's
    (?=^[^c]*c[^c]*$) ## One c and no other c's
    ^.{3}$            ## Exactly three chars
/x and print "$_: matched" for 'aaa'..'ccc';;

abc: matched
acb: matched
bac: matched
bca: matched
cab: matched
cba: matched
[download]

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

"Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."

Comment on Re: REgular expression to check the string that allows "a","b" and "c" to occur only once in any order. Download Code

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Re^2: REgular expression to check the string that allows "a","b" and "c" to occur only once in any order. by bart (Canon) on Dec 11, 2007 at 13:25 UTC
This looks like overkill. If a string is required to contain all of an "a", a "b" and a "c" and its length is limited to 3, then it can only contain one of each. So this ought to suffice: `/^(?=.a)(?=.b)(?=.*c).{3}\z/` [download] Of course, yours is the way to go if the length is not limited to 3.	[reply] [d/l]
Re^3: REgular expression to check the string that allows "a","b" and "c" to occur only once in any order. by BrowserUk (Patriarch) on Dec 11, 2007 at 14:55 UTC
Agreed, for the simple case, but it trivially extends to any number of unqiue characters within strings of a specified length. (Think crossword, hangman etc. :) Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply]