#!/usr/bin/perl
while($line = <DATA>){

@valid_entities= ('<a>','<abbr>','<acronym>','<br>');
my %htmlenties = map { $_ =>1 } @valid_entities;
#$line =~ s/(<\w*?>(?![^<\w*?>]*<\/\w*?>))/$1/g;
#$line =~ s/<\w*>(?![^<\/\w*>]*>)/&lt;/g;
$line =~  s/(<(\w*?)>)/exists $htmlenties{$1} ? $1 : defined ($2) ? "&
+lt;$2&gt;" : "&lt;"/eg;
print $line;
}

__DATA__
<helloe>How r u <a> www.google.com</a>
<hi>How r u </hi><et,-2><><br/>

[download]
How to convert character '<' to '&lt;' and '>' to &gt; for all the characters which is not present in the array
and only if it doesnot have a closing end tag. in the above example, the output should look like 
&lt;helloe&gt;How r u <a> www.google.com</a>
<hi>How r u </hi>&lt;et,-2&gt;&lt;&gt;<br/>

[download]

In reply to convert characters by Anonymous Monk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


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