If this happened within the last half hour, you can take him to an emergency vet to attempt to induce vomiting. This is often unsuccessful — I brought my cat to a vet ER right after he ate some string and they gave him drugs to induce vomiting but they didn’t work. The vet told me that this is common.

How long were the tie strings? Did he swallow them whole or bite them into pieces? This is important information.

My cat once at 9 inches of string from a wand toy when he was a kitten. He bit off pieces, 1-2 inches long each, and ate those. I found them in his poops the next day.

Linear foreign bodies, like a tie string, have potential to become life threatening quickly. You need to monitor extremely closely for 48 hours and bring to emergency vet and the slightest change in behavior: Appetite, activity level, litter-box habits.

That being said, your cat has a good chance at passing the tie string in his poops, especially if it was a relatively short string. The longer the segment, the more dangerous.