Text change across multiple files

#! /usr/bin/perl -w
use strict;
$^I=".bk";
while (<>) {
    $_ =~ s#rico.js#NiftyCube/niftycube.js#;
    print $_;
}
#run it like this: ls *html|xargs perl update.pl
 
 
 
#Here are some other versions of the same kind of thing:
#First version:
#code snippet to search-and-replace a group of files...
$^I=".bk";    # Create a backup
while (<>) {
	s/'/'/gi;
	print $_ ;
}
 
#Second variation: read from a list of files
#Assumes that name of list_file is first command line argument
#Also assumes we are reading a file with one URL on each line
while (<>) {
    chomp(my $url = $_);
    if ($url ne "") {
	grabit($_, $tag_type, $local_directory, $extensions);
	print $url . "\n";
 
    }
}
 
 
#Third variation: read a whole file into an array
my $input_file= shift;
open(WHOLEFILE_HANDLE, $input_file) || die("Couldn't open $input_file\n");
my @whole_file=<WHOLEFILE_HANDLE>;
foreach my $i (@whole_file) {
  print "$i";
}