That will match everything from the first abc to the first def, not not everything starting from the closest abc (which I believe is what the OP wants).

But it can be adapted, of course: 

m{
  (
     ^abc$
     (?:(?!^(?:def|abc)$).)*
     ^def$
  )
}smx

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In reply to Re^2: How do I match the closest of repeated strings? by moritz
in thread How do I match the closest of repeated strings? by Anonymous Monk

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