Thanks to everyone for working solutions provided. To further refine the OP, as I tried to simplify for the sake of clarity : Consider : 

#!/usr/bin/perl -w

use strict;

while ( <DATA> ) {


        s/ angle brackets between element pairs / instead make square 
+bracketed /


        print $_ . "\n";


}

__DATA__

<sometag> my data here </sometag>
<anothertag> further text </anothertag>
<furthertag> not good as contains <this> in angle brackets </furtherta
+g>
<byetag> another possibility is <more> <than> one <angle pairs> in her
+e </byetag>

[download]
As I can no longer specify (more|less) as fixed patterns ( as per ikegami hunch ) Im again struggling to apply what is demonstrated to my actual data... Required output : 
<sometag> my data here </sometag>
<anothertag> further text </anothertag>
<furthertag> not good as contains [this] in angle brackets </furtherta
+g>
<byetag> another possibility is [more] [than] one [angle pairs] in her
+e </byetag>

[download]

In reply to Re^4: Negating a regexp by jxh
in thread Negating a regexp by jxh

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