ascii85 encoder in perl

I got bored, here's an ascii85 encoder in perl (Adobe's take on it, anyway). check out wikipedia for more info.

use strict;

local $/;
my @foo;
print "<~";
@foo = unpack("C*", <>);
while (scalar(@foo) > 0) {
    my (@a, @buf, $x, $i);
    @a = splice(@foo, 0, 4);

    $x =
      (defined($a[0]) ? ($a[0] << 24) : 0) | (defined($a[1]) ? ($a[1] << 16) : 0) |
      (defined($a[2]) ? ($a[2] << 8)  : 0) | (defined($a[3]) ? ($a[3] << 0)  : 0);
    if (@a == 4 && $x == 0) { print "z"; next; }
    for $i (1 .. 5) {
        $buf[ 5 - $i ] = chr(($x % 85) + 33);
        $x /= 85;
    }
    print @buf[ 0 .. scalar(@a) ];
}
print "~>\n";