Note that the code above is doing roughly the same as:

$ ls /path/*.log | grep -v filename_exclude_pat | xargs grep -h line_include_pat >output.txt

right, but note also that the above is doing roughly the same as (a bit expensive as it process every line of unneeded files even if skip them):

   perl -lne 'next if $ARGV=~/filename_exclude_pat/;print if $_=~/line
+_include_pat/' *.log > output.txt
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L*