I've looked at several sets of instructions for ABC since my last post, That doesn't make me an expert, but all instructions including Mudcat's conform in a very rational manner with standard notation.

Don't know about the dotted bits, but the notation programs that I use (Finale Sibelius, G7 Guitar Pro) have settings to adjust the timing on swung quavers.

I would read the example as

Play A, repeat A, play B, repeat the tune from the beginning (on playing through again the repeat signs are ignored unless there are other instructions). This gives AABAB

Stu