What does $# stand for?

Kiko has asked for the wisdom of the Perl Monks concerning the following question:

Hi All,
I'm editing a script that has the following:

my @missing;
foreach my $f (@fields) {
  if ($account{$f} eq undef) {
    push(@missing, @acct_fields{$f});
  }
}
[download]

I understand what this is doing, but the following part that throws me off...although i can assume what it's doing i want to know how it actually works:

if ($#missing > -1) {
  $" = ', ';
  do something....
}
[download]

Thanks in advance for your help.
-Kiko

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Re: What does $# stand for? by tstock (Curate) on Oct 15, 2001 at 00:00 UTC
$#array returns the last index in a array. So, one less than the number of elements in a array. The code above is pretty ugly, and I would replace it by `if (scalar @missing)` [download] other examples: `scalar @array == ($#array + 1) # is always true unless you redefine where the index starts. for my $i (0..$#array) { # loops through the array by index number }` [download]	[reply] [d/l] [select]
Re: Re: What does $# stand for? by Fletch (Bishop) on Oct 15, 2001 at 00:43 UTC
Actually the `scalar` in the first case isn't necessary since boolean context is (more or less) scalar context as is shown with the code below. `@a = (); print "try 1\n"; print "Has elements\n" if @a; push @a, 1; print "try 2\n"; print "Has elements\n" if @a;` [download]	[reply] [d/l]
Re: What does $# stand for? by mischief (Hermit) on Oct 15, 2001 at 19:31 UTC
You might also want to look at perlvar if you come across any special variables you don't recognise in the future.	[reply]
Re: What does $# stand for? by gothic_mallard (Pilgrim) on Oct 15, 2001 at 21:02 UTC
I guess it might be worth noting a little caveat here that has caught innumerous novices in their first brushes with perl. Many people tend to forget in the heat of the moment that $# gives you the last index of the list - not the number of elements in it. Because of this: `$#list` won't give you the same result as `scalar @list`. This, I will admit, caught me a fair few times when I was starting out. Just a simple thought, probably beneath most of you guys out there, but one worth remembering ;)	[reply] [d/l] [select]