In that case, I'd check the end of the buffer for digits, and if there are any, trim them off and save them to prepend to the next buffer that you read in. But you don't want to do that if it's the final 0 in the file, so I have some if statements in here. There's probably a more elegant way to do some of this, but I think this will handle it correctly:

#!/usr/bin/env perl
use 5.010; use strict; use warnings;

my $l;               # chunk of a line
my $tiny_buffer = 8; # tiny buffer for testing
my $leftover = '';   # leftover, possibly partial number at end of buf
+fer
while ( read DATA, $l, $tiny_buffer ) {
    $l = $leftover . $l;
    say "        ;$l;";
    $leftover = '';
    if( $l =~ s/(\d+)$//g ){
        if( $1 == 0 ){
            $l .= '0';
            $leftover = '';
        } else {
            $leftover = $1;
        }
    }
    for (split ' ', $l) {
        if ( $_ == 0 ) {
            say 'Reached a zero';
        } else {
            say "; $_ ;";  # process a number
        }
    }
}

__DATA__
1 2 3 4 5 6 7 8 99 1 2 3 4 5 6 7 8 9 0
1 22 3 4 5 6 7 8 99 1 2 3 4 5 6 77 8 9 0
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