A query was posted recently on a list on how to convert date formats in the
form of "month/day/year" into a more standard unambiguous "year-month-day".
I dabbled in Perl a very long time ago and so thought I'd take a look. After
searching the Internet and some practice, here is my stab at it. For an
example csv text file, for tabular data in this case:

COLA,DATE,COLB,COLC
xxxx,12/15/2021,xxxx,xxxx
xxxx,01/14/2022,xxxx,xxxx

The following Perl script will flip the order.

---------------------------------------------------------------------------
#!/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);
---------------------------------------------------------------------------

We now have:

COLA,DATE,COLB,COLC
xxxx,2021-12-15,xxxx,xxxx
xxxx,2022-01-14,xxxx,xxxx