Use a negative look-ahead: 
$_ = "dog 789 cat dog dog bird cat wonder dog frog cat";

my @finds = /(dog(?:(?!dog).)*?cat)/g;

say Dumper \@finds;

[download]
Outputs: 
[
  "dog 789 cat",
  "dog bird cat",
  "dog frog cat"
]

[download]

In reply to Re: Rematching within a regular expression by Anonymous Monk
in thread Rematching within a regular expression by jeff987

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