Your code match the first occurrence of [a-z] in every element in @ARGV, and returns occurrences that occur at least as many times as elements in @ARGV. Sorry -- this is nothing like the original requirements.
P.S. Helpful hint: Even if you are only determining whether the concept you are trying for is correct, any posted code that is not in the form of pseudo-code should be tested. You would have found that your code did not meet the requirements without having had to ask. Cheers.
UPDATE: As per the followup by Anonymous Monk, I did miss the inner while(){}. The only line that appears to still be wrong is the line that reads "$found{$1} = $i + 1;". The effect appears to be that only characters that show up in the last element of @ARGV will be returned. A small adjustment that would perhaps allow this code to work would be to replace the faulty line with "$found{$1}++;". One good addition that this code suggests is an in-case-sensitive match. In order for this to work however, the faulty line will need to read "$found{lc $1}++;" to ensure that the correct hash element is incremented.
