#!/usr/bin/perl -w
use warnings;
use strict;
my ($tag, %list);
while (<DATA>){
next unless /./;
if (/^(\w+)/){
$tag = $1;
next;
}
if (/^-- (\w+)/){
push @{$list{$tag}}, $1;
}
}
for my $type (@{$list{main}}){
if ($list{$type}){
for (@{$list{$type}}){
print "main $type $_\n";
}
}
else {
print "main $type\n";
}
}

__END__

main
-- check
-- check1

check
-- computing
-- net

check1
-- computing2
-- net2

computing
-- community

The output should be 

main check computing community
main check net

main check1 computing2 
main check1 net2

But the output is coming as below:

main check computing1 
main check net

main check1 computing2 
main check1 net2