nah, it is your code that's not working. You assign a list to a scalar (not meant to store a list, see perlintro) and perl, trying what's possible, takes the first scalar value off that list and stores it in $data. Check that variable:

my $data = 'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'

    print $data;

A
[download]

See?
So what was your intention? Use an array? Put quotation marks into a string? I cannot tell from your question.

Cheers, Sören