thor,
I am not sure where you are running into the newline problem. I am betting it is with <>/readline. That is because they define a record by looking at $/ (see perldoc perlvar). PerlIO::via allows you to define your own buffering methods, but readline is still going to return records from the buffer by looking at $/. I don't think you are going to be able to use PerlIO::via to change that behavior. Notice the comment: 
package rdw;
use strict;
use warnings;

sub PUSHED { bless \*PUSHED,$_[0] }
sub FILL {
    my ($length, $record);
    read $_[1], $length, 1;
    return undef if eof $_[1];
    read $_[1], $record, $length;
    # uncomment next line to see it is actually working
    # print "$record\n";
    return $record;
}
sub WRITE { return undef }

package main;

open( my $in, '<:via(rdw)', 'foo.txt' ) or die $!;
while ( <$in> ) {
    print "$_\n";
}
__END__
# foo.txt - output is aababc
1a2ab3abc

[download]
If I guessed correctly, there are other ways to do it - speak up.

Cheers - L~R

In reply to Re: PerlIO::via FILL subroutine question by Limbic~Region
in thread PerlIO::via FILL subroutine question by thor

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