Scroll to navigation

dynamic(3) User Contributed Perl Documentation dynamic(3)


PerlIO::via::dynamic - dynamic PerlIO layers


 open $fh, $fname;
 $p = PerlIO::via::dynamic->new
  (translate =>
    sub { $_[1] =~ s/\$Filename[:\w\s\-\.\/\\]*\$/\$Filename: $fname\$/e},
   untranslate =>
    sub { $_[1] =~ s/\$Filename[:\w\s\-\.\/\\]*\$/\$Filename\$/});
 $p->via ($fh);
 binmode $fh, $p->via; # deprecated


"PerlIO::via::dynamic" is used for creating dynamic PerlIO layers. It is useful when the behavior or the layer depends on variables. You should not use this module as via layer directly (ie :via(dynamic)).

Use the constructor to create new layers, with two arguments: translate and untranslate. Then use "$p-"via ($fh)> to wrap the handle. Once <$fh> is destroyed, the temporary namespace for the IO layer will be removed.

Note that PerlIO::via::dynamic uses the scalar fields to reference to the object representing the dynamic namespace.


A function that translate buffer upon write.
A function that translate buffer upon read.
Use "READ" instead of "FILL" for the layer. Useful when caller expect exact amount of data from read, and the "untranslate" function might return different length.

By default "PerlIO::via::dynamic" creates line-based layer to make "translate" implementation easier.


Chia-liang Kao <>


Copyright 2004 by Chia-liang Kao <>.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

See <>

2017-10-03 perl v5.38.2