#!/usr/bin/perl

# https://perlmonks.org/?node_id=1221282

open my $fh, '<', \<<END;
###### test.txt########
sample AA
sample BB
Not sample CC
good boy
good yyy
bad aaa
END

local $/ = \1e6; # or bigger chunk depending on your memory size
while(<$fh>) # read big chunk
  {
  $_ .= do { local $/ = "\n"; <$fh> // ''}; # read any partial line
  push @sample, /^sample\s+(\S+)/gm;
  push @good, /^good\s+(\S+)/gm;
  }
close($fh);
print "sample = @sample\n  good = @good\n";

##</code><code>##

sample = AA BB
  good = boy yyy