use strict;
use warnings;
$_ = <<EOF;
abc:
  asdf1
  asdf2

def:
  asdf3

ghi:
  asdf4
  asdf5
EOF
my @tmp  = split /^(\w+:)/m, $_, -1;
my $hdr  = shift @tmp;
my @list = ($hdr) if defined $hdr && $hdr ne "";
push @list, shift(@tmp) . shift(@tmp) while @tmp;
my $cnt = @list;
$" = "><";
print "cnt=$cnt, values=<@list>\n";