There are some wonderfully inventive solutions already posted. But I would offer something a bit simpler...

#!/usr/bin/perl -w
use strict;

my (@desc, @data);
while (<DATA>) {
   next if /Description:/;
   last if /Data:/;
   push @desc, $_;
}
@data = <DATA>;


# DONE. Check results:
print "desc array\n", @desc;
print "data array\n", @data;

__DATA__
Description:
yada_d1
yada_d1
yada_d1
yada_d1
Data:
yada_d2
yada_d2
yada_d2
yada_d2
[download]

Update: Or, more concisely (but less readable at-a-glace)...

my (@desc, @data);
my $line = <DATA>;           # Throw away first line
push @desc, $line while ($line = <DATA>) !~ /Data:/;
@data = <DATA>;
[download]

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"Perl is a mess and that's good because the
problem space is also a mess." - Larry Wall