gistfile1.pl

use warnings;
use strict;

use Storable;

sub random_sequence {
    my @nuc = ( 'A' , 'T' , 'C' , 'G' );
    my $DNA;
    $DNA .= $nuc[rand @nuc] for 1..50;
    return $DNA;
}

my %DNAsequences;
for my $i (1..10){
    $DNAsequences{'DNA'.$i} = random_sequence();
}

store \%DNAsequences, 'file';

gistfile2.pl

use strict; 
use warnings;
use Storable;

my $dataref = retrieve( 'file' );


while( my ($key, $value) = each %{$dataref}){
    foreach my $base (qw/A C G T/){
        my @count = ($value =~ /$base{4}/);
        if(@count){
            print "Run (", $base x 4, ") found ", scalar @count, " times in $key\n";
        }
    }
}