If the bottleneck is on the sorting step, try using Sort::Key: 
use Sort::Key qw(nkeysort_inplace);

nkeysort_inplace { /(\d{2}):(\d{2}):(\d{2})\.(\d{3})/ and "$1$2$3.$4" 
+} @lines;

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In reply to Re: How to improve speed of reading big files by salva
in thread How to improve speed of reading big files by korlaz

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