#!/usr/bin/perl
use warnings;
use strict;
use 5.012;

# 902200

my @lines = qw(
	>seq1
	ASDFGHASDFGHJ
	ERTYUIOOIUYLK
	NBGFEWERTY
	>seq2
	BGTNHYMJUKOPK
	MNBFSDFGHJ
	>seq3
	USE_STRICT&USE_WARNINGS
	lastline
);


my $line;
my ($DNA, $seq);            # descriptive var names
my %all_hash = ();
for my $line (@lines){      # insert after this line, see update 2
        chomp $line;
        if ($line =~ /^>(seq\d)/ ) {  # captures seq# withOUT the '>'
                $seq = "$1\n";
		     say "\n\$seq: $seq";  # useful for debug; otherwise, not
        } else {
			
                $DNA = "$line\n";
		    say "\$DNA: $DNA";
        }
		no warnings;    #otherwise, warns 'unitialized' for the first $DNA
        $all_hash{ $seq } .= $DNA;    # concat $DNAs, which now 
                                      # have '\n's restored for readability
		use warnings;
}

print "\n =============== \n";

print %all_hash;

##</code><code>##

$seq: seq1

$DNA: ASDFGHASDFGHJ

$DNA: ERTYUIOOIUYLK

$DNA: NBGFEWERTY


$seq: seq2

$DNA: BGTNHYMJUKOPK

$DNA: MNBFSDFGHJ


$seq: seq3

$DNA: USE_STRICT&USE_WARNINGS

$DNA: lastline


 ===============
seq1
ASDFGHASDFGHJ
ERTYUIOOIUYLK
NBGFEWERTY
seq3
USE_STRICT&USE_WARNINGS
lastline
seq2
BGTNHYMJUKOPK
MNBFSDFGHJ