Sure, easy; like the man said, just use tie:

package Tie::FixedArray;
use Carp;

    sub TIEARRAY  {
                    my @new = (undef) x $_[1];
                    bless \@new, $_[0]
                  }

    sub FETCHSIZE { scalar @{$_[0]} }
    sub STORE     {
                    croak "Element out of bounds$!"
                        if (abs($_[1]) > @{$_[0]});
                    $_[0]->[$_[1]] = $_[2]
                  }
    sub FETCH     {
                    croak "Element out of bounds$!"
                        if (abs($_[1]) > @{$_[0]});
                    $_[0]->[$_[1]]
                  }
    sub EXISTS    { exists $_[0]->[$_[1]] }
    sub CLEAR     { @{$_[0]} = (undef) x @{$_[0]} }
    sub DELETE    { delete $_[0]->[$_[1]] }
    sub SPLICE    {
                    my $self = shift;
                    croak "Elements can't be removed from fixed length
+ arrays$!"
                        if (@_ < 2);
                    if (@_ > 2) {
                        my ($off,$len) = (shift,shift);
                        croak "Element out of bounds$!"
                            if ( (abs($off)+$len) > @{$self});

                        croak "Elements can't be removed from fixed le
+ngth arrays$!"
                            if ($len > @_);
                        croak "Elements can't be removed from fixed le
+ngth arrays$!"
                            if ($len < @_);
                        return splice (@{$self},$off,$len,@_);
                    }
                    elsif (($_[0] == 0) && ($_[1] == 0)) {}
                    else {
                        croak "Elements can't be removed from fixed le
+ngth arrays$!"
                    }
                  }

    sub STORESIZE { croak "Elements can't be added/removed to fixed le
+ngth arrays$!" }
    sub PUSH      { croak "Elements can't be added to fixed length arr
+ays$!" }
    sub POP       { croak "Elements can't be removed from fixed length
+ arrays$!" }
    sub SHIFT     { croak "Elements can't be removed from fixed length
+ arrays$!" }
    sub UNSHIFT   { croak "Elements can't be added to fixed length arr
+ays$!" }
    sub EXTEND    { croak "Fixed length arrays can't be extended$!" }

package main;
use strict;
use warnings 'all';

# 4 element fixed array
my $object = tie my @somearray,'Tie::FixedArray', 4;
$somearray[3] = 'hi';
print $somearray[3];
$somearray[5] = 'hello!' # watch it crash and burn!
[download]

Update: Accidentally mixed up carp and croak. Fixed.
Update: Fixed splice mistake mentioned by theorbtwo.