The text file being read has 3 columns, the first of which is non-numeric. If I specify the variables with foreach ... would that accomplish the same thing?

Sorry, my mistake. However, I'd stick with while rather than foreach. There is simply no benefit to filling memory with an entire file (however big) if you can only use 1 line at a time: 

while( <INTERVAL> ) {
     ## ignore the first field on each line
     my( undef, $start, $end ) = split "\t", $_;
...

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In reply to Re^5: A question About Array Indexing by BrowserUk
in thread A question About Array Indexing by ccelt09

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