#!/usr/bin/perl

use strict;
use warnings;

while (<DATA>) {
    s/(<%(?:[^%]+|%[^>])*%>)|'/$1 || ""/eg;
    print;
}


__DATA__
Leave this line alone.
Remove this quote ' and these two quotes '' from this line.
Leave <% the first quote ' %> alone, but remove the second ' one.
Remove from <% an open but not closed ' tag.
' Leading quote?
<% Multiple ' tags %> ' on one ' <% line ''' work  %> too ' !

[download]

Running this gives: 

Leave this line alone.
Remove this quote  and these two quotes  from this line.
Leave <% the first quote ' %> alone, but remove the second  one.
Remove from <% an open but not closed  tag.
 Leading quote?
<% Multiple ' tags %>  on one  <% line ''' work  %> too  !

[download]

In reply to Re: silly regex question by Abigail-II
in thread silly regex question by batkins

Title:
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and:  <code> code here </code>
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