Something like this then?

m/
  \A
  [[:alpha:][:digit:]]
  [[:alpha:][:digit:]-]*
  \z
/x
[download]

Shouldn't that be

m/
  \A
  (?:
    [[:alpha:][:digit:]]
    [[:alpha:][:digit:]-]*
  )?
  \z
/x
[download]

Your version requires that at least one character be present.

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

'\w' allows the non-alpha 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 '$'). Since I understood the OP's criteria to not permit any sort of space or special character, the solution is to use '\z' instead of '$'.

Update: As pointed out by Roy Johnson, \w also matches numeric digits, so the use of \d is redundant.




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

Thanks.. a lot....