It is possible to do with one regexp.

local our @matches;
$str =~ /
   (?{ [] })
   ^foo
   (?:
      \s+ m
      \s+ (\d+)
      (?{  [ @{$^R}, $^N ]  })
   )+
   \s+ bar
   (?{  @matches = @{$^R}  })
/x;
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Didn't say it was nice.