30-35 csv files ... each file is very big containing around 8-9 k lines.... taking time around 25-30 minutes

35 * 9000 = 315000 lines. That is not big. This shows perl processing 40 million lines in just over 10 seconds:

C:\test>wc -l bigfile
40000000 bigfile

[11:29:51.26] C:\test>perl -nlE"}{say $." bigfile
40000000

[11:30:02.41] C:\test>
[download]

So, the cause of your slow processing is not Perl, nor the size of those files, but whatever you are doing in your script. Throwing parallel processes or threads at it should be your last resort, not your first.

Your first resort should be correct whatever is wrong with your code that is causing it to be so slow. The quickest way to do that would be to post the code and let us help you with it.