In order to avoid potential mismatches of the field name and pack template values, I would think about using a hash to generate both the unpack template and the field names. The only problem is hashes are not stored in any particular order. To combat this, one could store the "hash" in an array, and separate the keys and values "manually." Example:

my @fields = qw(Year         A2
                Month        A2 
                Day          A2
                Request_Seq  A4
                Request_Type A2
                Record_Seq   A2
                Record_Data  A1486);

my @keys   = map $fields[$_], grep $_%2==0, 0 .. $#fields;
my @values = map $fields[$_], grep $_%2==1, 0 .. $#fields;

my %data; # bad name. we should know better. ;)
@data{ @keys } = unpack join("", @values), $foo;
[download]

Alternatives to this include, but are not limited to:

• Use a tied hash that maintains order, such as Tie::IxHash.
• Use a normal hash, but also keep along an array that is used to sort the hash keys and values. This is essentially what a tied hash would do for you, automatically.
• Some other extremely clever solution I have not thought of.