{  package PathCat; 
  use warnings; use strict;
  use 5.12.0;
  our @ISA=qw(Exporter);
  our @EXPORT=qw{pathcat Set_sep($) Fs_path_sep() pathcat(@)};
  use Exporter;
  our $_sep = '/';

  sub Set_sep ($) { $_sep = $_[0]; }
  sub Fs_path_sep () { $_sep }
  sub _fs_path_sep() { $_sep } 

  sub pathcat(@) {
    my $lval;
    shift while (! defined $_[0] ) and @_>=1;
    defined $_[0] ? (                   
      @_ >= 1 ? 
        $_[0] . (
          ( length ($lval=&path_cat($_[1], @_[2 .. $#_ ]))  and
            length $_[0] and  $_[0] ne _fs_path_sep ) ? 
          _fs_path_sep : '' ) . $lval : 
        $_[0]
        ) : $_[1] // ''
  }
  sub path_cat(@) { goto &pathcat } #old name compat

1;};