I would try parallelizing the process. Even running two processes on the same machine might help. Just divide the list.dat file into two, and try this: 
perl -MLWP::Simple -lne '...' list-part1.dat > results-1.txt &
perl -MLWP::Simple -lne '...' list-part2.dat > results-2.txt &

[download]
I have a feeling a lot of the running time is being spent waiting for the remote sites to accept the connection and respond.

In reply to Re: Question: Fast way to validate 600K websites by pc88mxer
in thread Question: Fast way to validate 600K websites by lihao

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