A file with files inside it, all of the same structure. Have you heard of XML, mmmkay?

First I'd change Perls internal input record seperator ($/) variable to that mystery character and suck the file contents into an array... how big are the subfiles likely to grow? This is an issue if you machine is not a server.(or it could be)

If I understand you correctly:

There is a really nasty file with records and sub-records.
The records are delimited with a character, you can't find: (try using ord to find it, or a hex editor.)
The sub record has a delimiter IEA..after this delimeter you want to know how many characters there are:  $count = m/IEA(.)*$/g does the trick, I think. (This is a regular expression that will get you the number of characters from IEA to the end of the file.)

I suspect what you want is a lot simpler for Perl to do, but you've come from a less friendly language (but I'm far too polite to say that ;-)

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