The default sort behavior with strings is "ASCIIbetical," rather than alphabetical. ASCII-wise, the capital letters (as a group) come before the lowercase (as a group); thus "D" comes before "a."

So assuming you want to sort a list of words, what you want is:

# make it a "sort sub"

sub alphabetical {
    # compares lower-cased versions of the strings
    lc($a) cmp lc($b);

}

# to sort having defined this sub, you do
@list = sort alphabetical @list;
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Or, to avoid making a bunch of tiny little otherwise useless functions, sort also lets you use a block in place of a function:

@list = sort { lc($a) cmp lc($b) } @list
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