You don't need to slurp. Either the line matches the regex /^$date_regex/ or it doesn't. (I'm assuming there's no chance the middle of a record will match that regex.) 
perl -n -e '$count++ if /^REGEX/;}END{print "$count\n";' FILENAME

[download]

And, yes, 55mb will blow out a 3G+ RAM. You should expect a 10-1 to 20-1 increase in memory usage over disk size. This is Perl ...

  • In general, if you think something isn't in Perl, try it out, because it usually is. :-)
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In reply to Re: Pimp My RegEx by dragonchild
in thread Pimp My RegEx by heathen

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