after reading open, I realize that when in a sub the first is example is good because you dont have to worry about closing the filehandle - it simply goes out of scope. Does the same hold true when in MAIN? Do I not have to cose the fh? Or am I missing something?

I second that, but it's not limited to subs which introduce nothing but a "lexical scope", so the keyword here is the latter. For example you may have

for (@files) {  #
    open my $fh, '<', $_ or 
      (warn "$_: $!\n"), next;
    push @first_lines, scalar <$fh>;
}
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Or, consider the following example script that exploits open as a cheap way to parallelize a series of possibly slow operations:

#!/usr/bin/perl

use strict;
use warnings;

die "Usage: $0 <net>\n" unless @ARGV == 1;
# Rudimentary check on the argument
(my $net=shift) =~ s/\.0+$/./
  or die "Supply an IP of the form <#.#.#.0>\n";

print 'Begun pings at ' . localtime, "\n";
my @p;
open $p[@p], '-|', "ping -w 5 -c 5 $net$_"
  or die "Couldn't start ping for $net$_: $!\n" for 1..255;
undef $/;
print map <$_>, @p;

__END__
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Note:

• here you may want to do a stricter check on the argument to make this into a "serious" thing,
• lexical handles are not strictly required for this to work, but they make it easier,
• the way used to fill @p here is somewhat exotic: you may prefer something like

  my @p = map {
      open my $fh, '-|', "ping -w 5 -c 5 $net$_"
        or die "Couldn't start ping for $net$_: $!\n"; 
      $fh } 1..255;
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  Done this way, you don't even really need @p any more, you could just chain the two maps. Oh, but I'm digressing...

In any case, to answer your question: yes! "lexical filhandles" are closed automatically on scope exit. But there are situations in which you may need to explicitly close them. If I don't need to, I don't; others' opinion may vary: see e.g. philcrow's reply.

Also, a filehandle can hold more than regular files, and there's stuff you still have to explicitly close.