Something like this then?
m/ \A [[:alpha:][:digit:]] [[:alpha:][:digit:]-]* \z /x
Dave
m/
\A
(?:
[[:alpha:][:digit:]]
[[:alpha:][:digit:]-]*
)?
\z
/x
You could be right. But since the OP doesn't specify whether or not the string must contain at least one character, I'd say that there is sufficient ambiguity in the definition of the problem that there's about an equal chance that mine is right. Good observation. Now the OP can choose which meets his needs.
Dave
- beginning of the string
- followed by a single word or digit character
- followed by 0 or more word, digit, or dash characters
- followed by the end of the string
-- -- GhodMode
That allows the special character '_' (which is considered by Perl to be a "word" character). It also allows for a trailing '\n' in the string (the \n isn't "matched", but it's permitted by '$'). Since I understood the OP's criteria to not permit any sort of space or special character, the solution is to use '\z' instead of '$'.
Dave
Dave's exactly right! So, I'll recommend and explain something which combines our methods ...
/^[:alpha:][[:alpha:]\d-]*\z/I favor one-liners, but that's just a style preference. I changed my \w to [:alpha:], my ^ to \A, and my $ to \z per davido's recommendation, but I stuck with the \d because it's shorter and still works in this case. I left off the m at the beginning because that's the default anyway. I left off the x at the end because this regex doesn't use extended patterns (ref: Extended Patterns).
- \A : Beginning of the string
- [:alpha:] : One alphabetic character (ref: perlre
- [[:alpha:]\d-]* : 0 or more characters consisting of alphabetic characters, digits, or dashes
- \z : The end of the string
-- -- GhodMode
Your solution is still wrong as proposed:
/^[:alpha:][[:alpha:]\d-]*\z/
The first mistake is that [:alpha:], by itself isn't a character class. It won't compile as you've written it. It needs to be presented like this:
[[:alpha:]] ^_________^______Note the outer set of brackets.
The next problem is that the OP stated that the first character cannot be a hyphen character, but he didn't exclude numeric digits. Your solution will fail if the first character is a numeric digit.
Also, '^' matches at the beginning of a "line". That probably isn't an issue for this particular regexp, but it is worth noting that '^' is different from '\A', which matches at the beginning of a string.
If you really despise the /x modifier, and prefer to avoid [:digit:] for whatever reason (maybe less typing?), you could rewrite my original solution like this:
m/\A[[:alpha:]\d][[:alpha:]\d-]*\z/
But I think the version with the /x modifier is easier to read since it keeps individual anchors together, and everything else separate.
Dave