You're working much to hard: 

#! /usr/bin/perl -w

use strict;
use locale;

for my $s ( @{[ "_'nada_komo_el_'sol_", "_na'da_komo_el_so'l_" ]} ) {
    print $s;
    $s =~  s/(_)([^'][^_]+?)/$1'$2/g;
    print " : $s\n";
}

__END__
C:\test>junk57
_'nada_komo_el_'sol_ : _'nada_'komo_'el_'sol_
_na'da_komo_el_so'l_ : _'na'da_'komo_'el_'so'l_

[download]
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.
"I'd rather go naked than blow up my ass"

In reply to Re^3: Modifying the match position after each match by BrowserUk
in thread Modifying the match position after each match by pat_mc

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