#Perl 5 + [Perligata](//metacpan.org/pod/Lingua::Romana::Perligata), 175 bytes

147 bytes, plus 28 for `-MLingua::Romana::Perligata`

Use as `perl -MLingua::Romana::Perligata foo.pl`; input (from stdin) and output (to stdout) are underscore-separated strings of decimal integers. Tested on Strawberry 5.20.2 with version 0.6 of Perligata, released two days ago; I don't know whether it works with Perligata version 0.50.

    huic vestibulo perlegementum da.his _ scindementa da.per in his fac sic
    si recidementum hoc tum II fac sic ultimus cis
    hoc tum _ egresso scribe
    cis

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Obviously this is clear as a bell. In case it's not, run it with `-MLingua::Romana::Perligata=converte` instead of `-MLingua::Romana::Perligata`, and `perl` will, instead of running the script, output a translation into regular Perl:

     $_ = Lingua::Romana::Perligata::getline (*STDIN );
     @_ = split ( '_');
    for $_ (@_) {if ( ($_ % 2)) {last ( )}
    ;
    print (STDOUT $_, '_')}

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Golfing notes:

* It seems from the documentation that `ultimus si recidementum hoc tum II fac.` would work instead of `si recidementum hoc tum II fac sic ultimus cis`, saving 7 bytes. But it doesn't (it gives a "iussa absentia" error).
* Undocumented (but unsurprising), you don't need a space after `.`.
* (Also unsurprising,) `scinde` doesn't need a second argument, and uses `hoc`.
* Instead of `huic vestibulo perlegementum da`, I tried `-pMLingua::Romana::Perligata`, but couldn't get it to work.

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Just for kicks (although this whole answer was just for kicks):

* After cleaning it up to `Huic vestibulo perlegementum da. His lacunam scindementa da. Per in his fac sic si recidementum hoc tum II fac sic ultimus cis. Hoc tum lacunam egresso scribe cis.`, Google Translate gives `This court perlegementum grant. His gap scindementa grant. Through these, so if you do this, then 2 recidementum do so the last side. This was the gap as soon as write on this side.`.