my $fh = new IO::Uncompress::Gunzip "input file",
    or die "Cannot open file ..." ;

my $line = <$fh> ;

##</code><code>##


my $fh = new IO::Uncompress::Gunzip "input file",
                   Transparent => 1
    or die "Cannot open file ..." ;

my $line = <$fh> ;

##</code><code>##

sub rewind
{
    $_[0]->close();
    $_[0] = new  new IO::Uncompress::Gunzip $_[1],
                   Transparent => 1
    or die "Cannot open file ..." ;
}

rewind($fh, "somefile");