#!/usr/bin/perl

# searches for xx/yy/zzzz (month/day/year) date pattern and converts 
# to zzzz-xx-yy in a text file (csv in this case).

open(FH,"myfile.csv") or die "Can’t open file-$1";
open(WH,">new_myfile.csv") or die "Can’t open file in write mode- $!";

while(my $line = <FH>){
               $line =~s/(\d{2})\/(\d{2})\/(\d{4})/$3-$1-$2/g;
               print WH $line;
}
   
close(FH);
close(WH);