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Given this little snippet, it appears that the goal of the first loop is to remove all the lines that don't end with 0 and put those into an array. The next loop then reads that array. So, you're iterating over your data twice, but you don't need to. You've got 1 completely copy of the file in memory, and another mostly completely copy. It takes time to create and destroy those copies. You don't need to do that either.
open(IN,$my_file) || die "Can't open: $!"; while (my $line = <IN>) { next unless $line =~ /0\s*$/; $line =~ /^(\d+.?\d*)//; if ($1 > .5) { # etc, etc } }
here's the break down line by line
  • Open the file
  • Process each line in turn. So, we're not storing the whole thing in memory (takes time to allocate said memory)
  • The if $1 == 0 part of your first loop only kept lines that ended in 0 for @zeroat. Just test directly for the line ending in 0 and throw away the rest.
  • no need for the regexp to catch the last character, we already know it's a 0
  • Test only the > .5 part, again no need for the $2 == 0 since we already threw away every line that didn't end in 0.
  • Rest of processing
HTH

/\/\averick
OmG! They killed tilly! You *bleep*!!


In reply to Re: Processing large files many times over by maverick
in thread Processing large files many times over by dimmesdale

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