# decode_base64.pl
use MIME::Base64 qw(decode_base64);

open (B64, $ARGV[0]) || die "$!";
local $/;
my $base64_string = <B64>;
close B64;
my $filename;
if ($ARGV[0] =~ /.\.b64$/i) {
    $filename = substr($ARGV[0], 0, length($ARGV[0]) - 4);
}
else {
    $filename = "$ARGV[0].bin";
}
open (IMAGE, ">$filename") || die $!;
binmode(IMAGE);
print IMAGE decode_base64($base64_string);
close IMAGE;
print "output file is $filename\n";