Combine the garlic, jalapeno and vinegar in a bowl. Stir in the parsley, oregano, and lime juice. Whisk in the olive oil and season with salt and pepper. Mix well and set aside at room temperature to allow the flavors to marry.
Reserve 1/2 cup of the chimichurri to serve and marinate the pork in the rest. Put the pork and marinade in a sealable plastic bag and set aside in the refrigerator for 30 minutes.
Preheat an outdoor charcoal grill or oven broiler to high.
Remove the pork from the marinade, wiping off any excess. Season both sides with a generous amount of salt and pepper. Drizzle with olive oil and place on the grill. Grill the pork on the hottest part of the barbecue for 4 minutes per side, until well charred. Allow the tenderloin to rest for about 5 minutes prior to slicing. Spoon some chimichurri over the meat, drizzle with lime juice, garnish with parsley, and serve with the remaining sauce at the table.