How about if you do a two-stage process of elimination: (please see the 'Update' first). 

while( <IFILE> ) {
    next unless m/^[CKMPSWY]/;
    print OFILE unless /^(?:CP|K[LM]|ME|P[AM]|S[LZ]|WX|YZ)XX1/;
}

[download]

This sort of "optimization" is highly sensitive to the type of data, however, if lines starting with [CKMPSWY] are sparse, it will reject non-matches much faster.

Update: Uggh, my logic is backwards in that snippet. The point is that if you can reject non-matches earlier, with fewer cycles, you save a little time.

I also wanted to mention the "print late" philosophy. If you're IO bound, you might be better off storing a few dozen lines in a scalar and printing just once every few-dozen iterations instead of on every iteration. This will maximize the effectiveness of the OS's buffering.


Dave

In reply to Re: perl performance vs egrep by davido
in thread perl performance vs egrep by dba

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