I found how to trigger the poem last night (it's a debug function called by entity 11), and was writing about it, but I'll dump this first.
You seem to be using an old script dump. In the version I downloaded (it was probably part of the script decompiler package), "opCE" is a check storyline progression opcode. (The debug room text has a nice list labeling the different storyline values.) So it should display at "Masamune Dissapears". The variables referenced in that script are roomVars, local variables. Instead of "Character(4)", it's "ENTITY 4" - the NPC version not in the active party. So after you talk to him once at that point, it sets a temporary flag, switching it to the other dialogue, back and forth.
One of the major issues in reading event scripts - I don't know if the later Cross hackers have made correct dumps - is an inconsistency with if-statements. That's partially my fault for not understanding it back then.
do condition with two values.
if true continue with next opcode, jump otherwise.
The logic is
if X is
true, then run the following line(s) of code,
else jump. Due to my incorrect labeling of opcodes back then, not all if-statements conform to this pattern.
Using the jump-to points from the if-statements, and jump-statements within, you can break down the code into if-else blocks.
