Nice, I've just tested it and it works fine. Thank you, Hans.
Btw, are you gonna include those passages? I have some other samples in the
public domain (Shakespeare's Sonnets translations, etc.) in case you're
interested in including them.

Regards,

Jairo :)

El vie., 7 de ago. de 2020 a la(s) 04:02, Hans Hagen (j.hagen@xs4all.nl)
escribió:

> On 8/7/2020 9:59 AM, Jairo A. del Rio wrote:
> > The original in English, Ozymandias, by Percy Bysshe Shelley, is public
> > domain. I extracted the Spanish and French versions from Wikipedia,
> > which use a CC BY-SA 3.0 License.
> Ok, here is the more robust variant:
>
> \blank
> \ifnum\boxlines\EnglishBox=\boxlines\SpanishBox
>      \ifnum\boxlines\EnglishBox=\boxlines\FrenchBox
>          \ifnum\boxlines\EnglishBox>0
>              \dorecurse{\boxlines\SpanishBox}{%
>                  \dontleavehmode\llap{\hbox to 1.5em{\txx#1\hss}}%
>                                 \boxline \EnglishBox#1\par
>                  \dontleavehmode\boxline \SpanishBox#1\par
>                  \dontleavehmode\boxline \FrenchBox #1\par
>                  \blank
>              }
>          \else
>              No content found!\blank
>          \fi
>      \else
>          English and Spanish boxes mismatch!\blank
>      \fi
> \else
>      English and French boxes mismatch!\blank
> \fi
>
> Hans
>
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>