Well, you could:

use strict;
use warnings;

my $byte = qr/([0-9a-f]{2})/i;

while (<DATA>) {
    my $line = join '', /\b$byte\b/g;
    
    next unless length $line;
    print "$line\n";
}

__DATA__
00 0A EF 85 BA 8F AA BC
Wibble
00 0A EF 85 BA 8F AA BC
[download]

Prints:

000AEF85BA8FAABC
000AEF85BA8FAABC
[download]