Try running your script again after installing the new version 1.88_01 from CPAN.

You haven't shown the appropriate code to reproduce the issue, and the following works fine for me:

use warnings;
use strict;
use Data::Dumper;
use Net::SFTP::Foreign;
$Data::Dumper::Useqq=1;

die "Usage: $0 SSH_HOST\n" unless @ARGV==1;
my $sftp = Net::SFTP::Foreign->new($ARGV[0]);
$sftp->die_on_error("Unable to establish SFTP connection");

my $fh1 = $sftp->open("/etc/passwd") or die $sftp->error;
while (<$fh1>) {
    print Dumper($_) if /root/ || /wheel/ || /www/; 
}
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To get better help, register an account so that you can edit nodes if necessary (instead of posting several disjoint anonymous nodes) and show a Short, Self-Contained, Correct Example that reproduces the issue - for example you don't show how you create the $sftp object (I have to guess that it's an Net::SFTP::Foreign), and you don't tell us which line is 96. See also How do I post a question effectively?

use common::sense;
# Supposed to be mostly the same, with much lower memory usage, as:

   # use utf8;
   # use strict qw(vars subs);
   # use feature qw(say state switch);
   # use feature qw(unicode_strings unicode_eval current_sub fc evalby
+tes);
   # no feature qw(array_base);
   # no warnings;
   # use warnings qw(FATAL closed threads internal debugging pack
   #                 portable prototype inplace io pipe unpack malloc
   #                 glob digit printf layer reserved taint closure
   #                 semicolon);
   # no warnings qw(exec newline unopened);
use Net::SFTP::Foreign;
use Getopt::Std;
use Config::General;
use Fcntl qw(O_RDONLY :mode);
use boolean ':all';
use Data::Dumper;
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use common::sense; Ick!

While it does many good things, I avoid this module for a couple of reasons:

1. no strict 'refs'; is an uncommon sensibility. Use it only in those few blocks where it has value.
2. use utf8; is entirely reasonable in a web app; but, in a command line environment, it completely ignores your terminal's settings and decodes your command line as utf8, no matter how inappropriate.
TJD

I agree on no strict 'refs';, but am not sure what "use utf8; ... decodes your command line as utf8" is supposed to mean (also considering this isn't a oneliner). Are you maybe thinking of use open qw/:std :utf8/; or perl -C instead? (see utf8 vs. open vs. -C)

[... some stuff here ] 

if ( $var eq "*" ) {
   $file = "name*"; # is some real file with an Asterix to search only
+ on them in the real code
   my $ls = $sftp->ls (wanted => qr/$file}/ )  or die "unable to retri
+eve directory: ".$sftp->error; 
   print "$_->{longname}\n" for (@$ls);

} else { 
   $file = "realname.ext"; # existing file 
   say $file;
   # reading - default method - from the remote file
   $fh1 = $sftp->open("$file") or die $sftp->error;
   while (<$fh1>) {
     print if  /ORA-/ || /Fehler/ || /ORACLE-Fehler/; 
     # my $last = $_;
     # print $last;
   }
exit 0;
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