use strict;
use warnings;

my @a = map { s/\s*(#.*)?$//g; $_ } <DATA>;

my @b;
while (local $_ = shift @a) {
	if (m/\D(\d+)-(\d+)(?:\D|$)/) {
		my $range = "$1-$2";
		foreach my $i ($1..$2) {
			local $_ = $_;
			s/(\D)$range(\D|$)/$1$i$2/;
			push @a, $_;
		}	
	}
	else {
		push @b, $_;
	}
}

print join("\n", @b);

__END__
172.17.119.2 # Comments are here...
172.17.119.4-5 # Comments are here...
172.19-21.254.2-3 # Comments are here...
192.168.1.1-3 # Comments are here...