use strict;

my $contents = do {local $/; <DATA>};
print get_chunk($contents);

sub get_chunk {
   my ($contents) = @_;
   my $start = qr|========= Summary of bfpr_catfl results ===\s*|;
   my $end   = qr|========= end ===\s*|;

   my ($chunk) = $contents =~ /$start(.*)$end/s; 
   return $chunk;
}

__DATA__
you won't see this
or this
========= Summary of bfpr_catfl results ===
you will see this
and this
========= end ===
you won't see this
or this
or that