while($line=<>) {
  ($key,$num1,$num2,$string,$num3,$stringnum) = split(/\s/,$line);
  $somehash{"$key"}{"$num1"}{"$num2"}{"$string"}{"$num3"}= $stringnum;
}
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that puts the data into a "hash", but probably not what you want.
whether you use a hash or array structure largely depends on the data available and the logic/processing required. sequential processing and lack of a random access key lends itself to an array structure. when you have a good logical random access key (not a record sequence number) and need to access the records non-sequentially, use a hash. a hash structure, or even a mix of hash and array structure may be suitable. but exactly what structure do you want? both approaches could be out the window if you have millions of records in the file, whereby some much smarter arrangement would be required to achieve the logic/processing required.
speaking of which..what is the required logic/processing for these records?