First, the assumption that a "more compact" Perl program will
execute faster is not true. In fact the opposite is often true!
The algorithm used will typically make far, far more difference.
Also aside from execution speed, Perl compiles at lightning speed
and whether you have a "one liner" or 1,000 lines usually makes
no real difference at all.
graff's cmpcol utility looks to be pretty flexible. If that
critter does all you need, then I think we're done.
I see that the content of the OP (original post) has been restored.
A few general comments on it related to performance:
1) In general, reading a line at a time and processing it right then
works out better than
slurping all the data into an array which is then later processed
line by line anyway. You start out by essentially
making a verbatim memory resident copy of both files. If they
are big files, this alone will take noticeable time. Aside from the
file I/O time, the construction (memory allocation) and copying of
the data into the array takes time.
2) For every line the first file, you cycle through all of the lines
in the second file. This can be very expensive execution time-wise!
This is a: #lines(file 1) * #lines(file 2) situation.
3) Going back to re-process the same data again and again is "expensive".
Perl split() is a nice critter, but this is not a "cheap" function. Every
trip through the file2 data (of possibly many trips) requires this
at each line.
4) To make your code faster, then general idea would be to "do something
very significant" with each line read and to the extent possible, don't
process the same data twice.
5) I would be thinking of making a data structure, an AoA or a hash table
for the first file (not a simple "verbatim" copy of that file) which
contains the "search or join term" and the complete line (for output).
Cycle through file2 just once. At each line, decide if there is a match or not
with some term in the file1 data structure. That way file2 is only processed
one time.
6) One technique that is sometimes overlooked, is that with Perl you can
build dynamic regex'es on the fly! You could build a single regex that
describes all of the terms in file1 and run that regex against each
sequential line of file2. my (@terms_found) =~ m/...huge regex.../g; Use the
"quote regex", qr syntax.
7) Another technique that is sometimes overlooked is the use of system
sort to simply the processing. If these are really big files, this idea
may work out also.
The possibilities to fine tune the performance are not endless, but many.
Some examples of your files as well as typical sizes would be very
appropriate. I think if you implement to step(5) of the above, the performance increase will be noticeable. Again, split() is great, but it is not a "cheap" function in terms of CPU. If you just put file2 into a better structure and didn't run split() so often, that alone would increase performance.