IO::Uncompress::Gunzip expects to be given valid and complete gzip data stream. If that doesn't happen, it fails.

I'll use the compressed data in $gzipped below to illustrate.

    use IO::Compress::Gzip qw(gzip);
    use IO::Uncompress::Gunzip qw(gunzip $GunzipError);

    my $data = 'I include only the bare bones because I tried somethin
+g';

    # Create some compressed data
    my $gzipped ;
    gzip \$data => \$gzipped ;
[download]

Lets start with the valid part. If I create data corruption in the compressed data stream, bad things happen

    my $corrupt = $gzipped;

    # Overwrite part of the compressed data with junk
    substr($corrupt, 10, 3, "BAD") ;

    gunzip \$corrupt => \$uncompressed
      or print "Cannot gunzip: $GunzipError\n";
[download]

That will output

    Cannot gunzip: Inflation Error: data error
[download]

If you get that, there is no point in continuing.

Next is a truncated data stream (which is what this ticket is all about).

    # truncate the compressed data
    my $truncated = substr($gzipped, 0, 10);

    gunzip \$truncated => \$uncompressed
      or print "Cannot gunzip: $GunzipError\n";
[download]

that will output this

    Cannot gunzip: unexpected end of file
[download]

In this instance, you can try to get more data, append to the input buffer ($truncated in this case) and uncompress the whole thing again. The only semi-valid use for this technique is when you are certain that you will eventually get a complete gzip data stream. That does not seem to be the case in this instance.