gistfile1.txt

# Here's the input, as an indented heredoc
my $string = <<~"_STRING";
	ABCD
	EFGH
	IJKL
	ABCD
	EFGH
	IJKL
	_STRING

# Open a filehandle on a reference to the string. Now you can read lines 
# of the string
open my($sh), '<', \$string;

# read a line, then the next two. Use chomp to get rid of the newlines.
# Reconstruct the string however you like.
while( <$sh> ) {
	chomp;
	my @next_two = map { scalar readline($sh) } 1 .. 2;
	chomp( @next_two );
	say "$_|" . join ",", @next_two;
	}