Scarborough,
That is Perl making your life easy. The intent is to prevent the programmer from having to keep track of indices. 
my @array = qw(one two three);

my $last_index = $#array;         # Index of last element (2)
my $last_element = $array[ -1 ];  # Value of last element (three)

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And then of course there is push, pop, shift, unshift to make your life easier as well.

Cheers - L~R

Update: Some other helpful things to remember 
my $count = @array;               # Number of elements (3)
$#array = 99;                     # Extend/Truncate array

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In reply to Re: What does $#variable mean? by Limbic~Region
in thread What does $#variable mean? by Scarborough

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