I have a process that research in a text two words (#par1, $par2) that could be in $distance, and highlight it in a text. I have the following regulars expressions 
$content =~ /\b($par1)(\W+(?:\w+\W+){1,$distance})?($par2)\b/i
$content =~ /\b($par2)(\W+(?:\w+\W+){1,$distance})?($par1)\b/i

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In fact is the same expression but with the words switched. I don't remember why I made separate but in the program where I use it works correctly. There's some reason but I'm not sure. Suddenly today the program starts to freezes and I found was because the second expression. The example that mades perl could not exit the evaluation of second regexp is: 
The words where "abbott" and "salud" and the maximum distance was 20.

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And the text was the following 
La mitad de las personas con VIH requiere de una atención  psicológica
+ y emocional derivada del impacto del diagnóstico o de las  consecuen
+cias de la propia infección, una cifra que dobla a la de la  població
+n general, según las conclusiones de las IV Jornadas de  Divulgación 
+sobre VIH que han reunido a unos doscientos profesionales,  pacientes
+ y estudiantes en el hospital  Reina Sofía de Murcia. En el  congreso
+, organizado por Amuvih en colaboración con el servicio de  Proyecció
+n Social y Voluntariado de la Universidad de Murcia y Abbott,  ha det
+erminado que las personas que viven con VIH demandan especialmente  a
+tención a su salud mental para mejorar su calidad de vida, "una  asig
+natura pendiente a pesar de los innumerables avances  farmacológicos"
+.

Entre otros factores, las jornadas establecieron  que en la situación 
+de "vulnerabilidad" de las personas con VIH  influyen "el propio diag
+nóstico, la comunicación de su situación a los  allegados, el inicio 
+del tratamiento, las fluctuaciones a lo largo de la  infección, la pé
+rdida de salud y deterioro físico, así como los efectos  adversos del
+ tratamiento".

Igualmente, otros factores  importantes son la pérdida de la motivació
+n, el hastío, el estigma y  rechazo, así como las nuevas parejas sexu
+ales, los cambios familiares,  laborales y sociales, entre otras cosa
+s, que derivan en "riesgo de  depresión mayor, trastorno distímico, t
+rastorno por ansiedad  generalizada o trastorno de pánico".

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In fact the first expression makes a match but when the program process the second expression the program freeze. In fact, in the intention to process accents the exacts words that compare are: 
$par1 = [a\xe0\xe1\xe4\xe2A\xc1\xc0\xc4\xc2]bb[o\xf2\xf3\xf6\xf4O\xd3\
+xd2\xd6\xd4]tt;
$par2 = s[a\xe0\xe1\xe4\xe2A\xc1\xc0\xc4\xc2]l[u\xf9\xfa\xfc\xfbU\xda\
+xd9\xdc\xdb]d;

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Note: To detect the correct number of words are between this two words I have to change the locale 
    use POSIX qw(locale_h);
    my $old_locale = setlocale(LC_CTYPE);
    setlocale(LC_CTYPE, 'ca_ES.iso885915@euro');
    use locale;

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Anybody think of any reason that could happen when in other cases the expression works correctly? You think the expression is wrong, or could be more simple? The code process the regular expression and if matchs after the content is highlighted. This the exact code 
        my $new_content = $content;
        if ($content =~ /\b($par1)(\W+(?:\w+\W+){1,$distance})?($par2)
+\b/i){
            my ($res1, $res2, $res3) = ($1, $2, $3);
            $new_content =~ s/$res1\Q$res2\E$res3/<$tag$class> $res1<\
+/$tag>$res2<$tag$class> $res3<\/$tag>/i;     
        } 
        if ($content =~ /\b($par2)(\W+(?:\w+\W+){1,$distance})?($par1)
+\b/i){
            my ($res1, $res2, $res3) = ($1, $2, $3);
            $new_content =~ s/$res1\Q$res2\E$res3/<$tag$class> $res1<\
+/$tag>$res2<$tag$class> $res3<\/$tag>/i;     
        }

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I have no idea how to resolve it, finally I have to disable this process temporally to highlight it because of freezing effect.

In reply to Problems searching and highlighting proximity words in a text by jrc

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