#!/usr/bin/perl -w
use strict;
use IO::Zlib;

my $tempFilename1 = "yeast.aa.Z";
my $tempFilename2 = "yeast.aa";

open (DATAFILE, ">>$tempFilename2")  
   || warn "Can't open uncompressed data file: $tempFilename2: $!";
   
my $fh = new IO::Zlib;
if ($fh->open("$tempFilename1", "rb")) {
    print DATAFILE <$fh>;
    $fh->close;
}