use strict;
use warnings;

my $head_re = qr/^(?:Heading Here|Another Heading):/;
my $end_re  = qr/^End of section:/;

while (<DATA>) {
    state $saw = 0;
    if (my $seq = /$head_re/ ... /$head_re|$end_re/) {
        if ($seq == 1) {
            s/^/\n/ unless $saw++;
        } elsif ($seq =~ /E0$/) {
            $saw = 0 if /$end_re/;
            redo;
        } else {
            s/^/  /;
        }
    }
    print;
}