use strict;
use warnings;

while (<DATA>) {
    print if (/d1/ .. /d4/);
}
__DATA__
a
b
c
d
d1
d2
d3
d4
a
b
d1
d2
d4
a
f
g
[download]

prints:

d1
d2
d3
d4
d1
d2
d4
[download]

What have you tried? This looks like something fairly simple...

Basically, I'd set a flag when I see d1, and unset it when I see d4. While the flag is set, push to the array. That's about three lines of code...

use strict;
use warnings;
my $flag = 0;
my $start = 'd1';
my $end = 'd4';
my @array;
while (<DATA>) {
  chomp;
  if(/$start/){
    $flag = 1;
    @array = ();
  }
  elsif(/$end/) {
    $flag = 0;
    print "@array\n";
  }
  else{
    push @array, $_ if $flag;
  }
}
[download]

Sounds like a job for Perl regular expressions.

while (<>) {
    if (/(d\d)/) {
        push @array, $1;
    }
}
[download]