Simple csv file parser, takes infile, adds a time where appropriate, writes to outfile. All should reside in the same directory.

gistfile1.txt

#!/usr/bin/perl

open INFILE, "fin2_tran.csv" or die $!;
open OUTFILE, ">fin2_out.csv" or die $!;

while (<INFILE>) {
  s/,(\d{4}-\d{2}-\d{2})(,[^,]+$)/,"$1 11:00:00"$2/;
  print OUTFILE;
}