I would be inclined to dip a long thin needle or wire into acetone, and insert it into the short end of the perforation (or where the knot is); wait a couple of minures, and push out from the opposite end.

I have had to try most or all of the previous methods, at one time or another. The only time I have broken a bead is when I impatiently tugged too hard—when I should have been pushing from the opposite end. Take your time and work on it bit by bit, and repeat as necessary.

JDA.