There is a telephonenumber format that looks about like (I hope I remember correctly):

$telephoneNumber =~ /^\+(\d\d)\-(\d+)(:?\-(\d+))+$;/
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where $1 +\d\d stands for the countrycode, $2 the areacode (=citycode), $3 the number, and maybe $4 for a sharing number (don't know the english word).

e.g: +49-69-44885599
or: +49-69-123-12345
(whereas the + is replaced by a local far distance call numbers, e.g. 00 in Germany, and I think 1 in the USA). But I'm not quite sure if this format is really a standard or not (will try to find the definition again; was something with ISDN-Number in X400 or the like).

Best regards,
perl -le "s==*F=e=>y~\*martinF~stronat~=>s~[^\w]~~g=>chop,print"