perl script to create de-normalized output file

I have a pipe delimited flat file which has 1 record per invoice-number. Per invoice records, there's header section, lines section (repeated multiple times - could go as much as 100 times) and the trailer section - something like this: HA1|HA2|HA3|L1-1|L1-2|L1-3|L1-4|L2-1|L2-2|L2-3|L2-4|T1|T2|T3 HB1|HB2|HB3|L1-1|L1-2|L1-3|L1-4|L2-1|L2-2|L2-3|L2-4|T1|T2|T3 The output file should like this: HA1|HA2|HA3|L1-1|T1|T2|T3 HA1|HA2|HA3|L1-2|T1|T2|T3 HA1|HA2|HA3|L1-3|T1|T2|T3 HA1|HA2|HA3|L1-4|T1|T2|T3 HA1|HA2|HA3|L2-1|T1|T2|T3 HA1|HA2|HA3|L2-2|T1|T2|T3 HA1|HA2|HA3|L2-3|T1|T2|T3 HA1|HA2|HA3|L2-4|T1|T2|T3 HB1|HB2|HB3|L1-1|T1|T2|T3 HB1|HB2|HB3|L1-2|T1|T2|T3 HB1|HB2|HB3|L1-3|T1|T2|T3 HB1|HB2|HB3|L1-4|T1|T2|T3 HB1|HB2|HB3|L2-1|T1|T2|T3 HB1|HB2|HB3|L2-2|T1|T2|T3 HB1|HB2|HB3|L2-3|T1|T2|T3 HB1|HB2|HA3|L2-4|T1|T2|T3 For someone with Perl Expertise - this should be pretty st forward script. The script should be well documented and maintainable and needs to run on Linux. Your work should be guaranteed to work as per requirements :)