Perl in place editing within a script (rather than one liner)

Question

So, I\'m used to the perl -i to use perl as I would sed and in place edit.

The docs for $^I in perlvar:

Answer 1

The edit-in-place behaviour that is enabled by the -i command-line option or by setting $^I works only on the ARGV file handle. That means the files must either be named on the command line or @ARGV must be set up within the program

This program will change all lower-case letters to upper-case in all CSV files. Note that I have set $^I to a non-null string, which is advisable while you are testing so that your original data files are retained

use strict;
use warnings;

our $^I = '.bak';

while ( my $file = glob '*.csv' ) {

  print "Processing $file\n";

  our @ARGV = ($file);

  while (  ) {
     tr/a-z/A-Z/;
     print;
  }
}