>>You are misinterpreting the {1,20} and {1,12}. These mean that the group preceding it is repeated between 1 and 20 or 1 and 12 times respectively. The expression you probably want is: ([A-Za-z0-9][A-Za-z0-9\-]{19})\-([A-Za-z0-9]{12})
>>
>>To break this expression down:
>>The first [A-Za-z0-9] indicates the first character must be A-Z, a-z, or 0-9.
>>The following [A-Za-z0-9\-]{19} indicates the next 19 characters must be A-Z, a-z, 0-9, or -.
>>The parenthesis around these two make it into a capturing group.
>>The next \- matches a literal hyphen.
>>The final ([A-Za-z0-9]{12}) matches 12 characters of A-Z, a-z, or 0-9.
>>
>>If any of the blocks can be variable length, change the {n} to {n,m} where n is the least number of times that block can repeat, and m is the most it can repeat. http://www.regular-expressions.info/refrepeat.html also provides more information on the variations of the repeating indicator.
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>Thanks, this is very valuable.
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>Basically, this is more readable I would assume for someone who tries to interpret this for the first time:
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>([A-Za-z0-9]{1}[A-Za-z0-9\-]{19})\-([A-Za-z0-9]{12})
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>So, at least, in the first part, we know it is only for character 1. Then, we have another filter for the next 19 characters.
>
>Or:
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>([A-Za-z0-9]{1}[A-Za-z0-9\-]{19})-([A-Za-z0-9]{12})
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>...if we ignore the \ which is only there to make sure the - is interpreted ok.

Yes, either of those should be equivalent. You may want to also add a ^ to the beginning and a $ to the end to ensure the matched string is from a single word and not a substring of a larger word. Depending on what you are doing with the regex, the parenthesis may also be unnecessary. They will store off those substrings as a match that can be retrieved later or used in a replace. If you are using the matching groups, you don't need them.