It was written:

    open(INPUT, "/usr/bin/gzip -d -c '$filename' |")
    open(OUTPUT, "| /usr/bin/gzip > '$filename'");
[download]

Make sure that you use a different value for $filename on each of these calls, or you (may|will) clobber the contents of the file you are trying to read, that is, unless you are using an OS with versioned files.

--MidLifeXis