I am trying to create a PerlIO::via layer (to be used with file handles opened for writing only) that appends a string (eg the string 'END') at the end of a file. So for example you should be able to do something like 
open my $fh '>:via(Append)','/some/file';
print $fh "Lorem ipsum dolor sit amet ";
close $fh;

[download]
and that would output the string "Lorem ipsum dolor sit amet END" to the file. So far I have tried the following: 
package PerlIO::via::Append;

sub PUSHED {
        my ($class,$mode,$fh)=@_;
        return -1 if $mode eq 'r' || $mode eq 'r+';
        my $buf='';
        bless \$buf,$class;
}

sub WRITE {
        my ($self,$buf,$fh)=@_;
        $$self.=$buf;
        length($buf);
}

sub FLUSH {
        my ($self,$fh)=@_;
        print $fh $$self or return -1;
        $$self='';
        0;
}

sub POPPED {
        my ($self,$fh)=@_;
        print $fh "\n";
}

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but that doesn't work, the print in POPPED fails. Any ideas?

In reply to Create PerlIO::via layer to append data at the end of a file by silly8888

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