You say you need the complete file in an array, but you may be able to rework what you're doing to avoid this. See if you can figure out some minimum amount of items from the file that you need to work on (e.g. the first two columns are the username and the frobnitz, the rest can be read on demand). Then either:

• throw the data into a DB or DBM file keyed by username/frobnitz
• preprocess the file once line by line building a hash of username/frobnitz to the offset returned by tell

Once you've done one of those things you process the list of keys, retrieving the other data as needed (by reading from a tied hash or using seek to move back and forth in the file).