Question

I am writing a Perl script to change all URLs within several files in one directory from camel case to lowercase.

e.g. from

   <a href="FooBar.html">

to

   <a href="foobar.html"> 

This test substitution correctly renames all URLs to foobartest.html as expected:

   s/^<a href=\"(.*?)\"/<a href=\"foobartest.html\"/g

But I am having difficulty in referencing the actual filename via the variable $1. An example of what I am trying:

   s/^<a href=\"(.*?)\"/<a href=\"\L$1\"/g

This substitution merely changes the link to . What am I missing?
You can probably tell I’m fairly new to Perl, and so any guidance would be much appreciated.

---

Full script for reading files within a directory and substituting (writing it as a one-liner does not work either, despite other substitutions working via one line):

#!/usr/bin/perl

use strict;
use warnings;

    chdir("/var/www/html/twiki_html") or die "$!";
    opendir (DIR, ".") or die "$!";
    my @files = grep {/.*?\.html/} readdir DIR;
    close DIR;
        {
        local @ARGV = @files;
        while(<>){
            s/^<a href=\""(.*?)\"/<a href=\"\L$1\"/g;
            }
        }

Answer 1

A simple one-liner:

perl -pwe 's/(?<=<a href=")([^"]+)(?=")/\L$1/' *.html

It will not change anything, just display the changes. So, when you are satisfied it works, you can add -i to the options to make changes to the files. Be aware that changes are irreversible. Use -i.bak to keep backups. E.g.:

perl -i.bak -pwe 's/(?<=<a href=")([^"]+)(?=")/\L$1/' *.html