How to perform search-and-replace within given $start-$end ranges?

Question

Say, a text file have many $start-$end pairs, and within each pair there are some text. I want Perl to find-and-replace all $patterns with the

Answer 1

Looking at your 'source' I would suggest the trick here is to set $/ - the record separator.

If you set it to a single space, you can iterate word by word. And then use a range operator to determine if you're within delimiters.

Example:

#!/usr/bin/env perl

use strict;
use warnings;

local $/ = ' ';

while (  ) {
   if (  m/START/ .. /END/ ) {
       s/bingo/okyes/g;
   } 
   print;
}

__DATA__
xx START xx bingo xx bingo xx END xx bingo xx START xx bingo xx END bingo

This prints:

xx START xx okyes xx okyes xx END xx bingo xx START xx okyes xx END bingo

You could probably accomplish this with a single regex. I'm going to suggest that you don't because it'll quite complicated and hard to understand later.