If I am reading hipowls's regex correctly it will be checking the negative look-ahead for every character between 'start' and 'end'. Just doing the look-ahead once should locate the last 'start' in a group then the .+? can run without keep checking after every character.

use strict;
use warnings;

my $string = <<'EOT';
start
start
start
go
one
end
start
start
start
go
two
end
EOT

my $rxGroup = qr
   {(?isx)
       (
           start
           (?!\nstart)
           .+?
           end
       )
   };

print qq{$1\n\n} while $string =~ m{$rxGroup}g;
[download]

The output.

start
go
one
end

start
go
two
end
[download]

I hope I am correct and this slight change will speed up your code.

Cheers,

JohnGG

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