I did some crude benchmarking and the only speedups for your regex I could find were:

1. Anchor the end of the regex with a $. 2-3%
2. Don't capture the inner group, use (?:\S+\s+) 3-4%
3. use study on $line before the if() statement 2-3%

A total benefit of 8-9% timing the match/assignment only, and I could only measure the changes by repeating the matching/assignment 1000 times for each line! Overall, not a great deal to be gained. For instance, just including the four print statements into the timing, even when redirecting the output to the null device, increased the time taken to process each line by 300%. Making the small savings I described above <1% in total.

You would gain more by

• not performing the substitutions of '|' for '_' which appeared nowhere in your test data.
• If your real data does need this processing, do it in one pass prior to breaking the line up.
• not slurping your data into a string and then spliting it to process it line by line.

  I realise this is only a test program, but if you are doing a similar thing on your real program, especially if the file is large, you would be much better off using while($line = <DATAFILE> ) {...}

Whatever differences the changes I described make, they are likely to pale into insignificance when compared to whatever you are doing with the data you have extracted from each line. Even just writing this to another file will completely marginalise any savings.