Thank you ikegami, I tried Capture::Tiny and it allows to nest wrapping of redirections for STDERR. Example code: 
#!/usr/bin/env perl
use strict;
use warnings;

use Capture::Tiny ':all';

sub innerAction {
    print STDERR "FIRST CAPTURE\n";  # to innerbuffer, works
}

sub handleInner {
    print STDERR "INNER before capture\n";
    
    my ($innerBuffer, @results) = capture_stderr { innerAction(); };
    
    print STDERR "INNER past restore\n";  
    # above goes to console or the outerbuffer, 
    #   it fails for outerbuffer when called from handleOuter
    
    chomp $innerBuffer;    
    my $no=1;
    foreach my $line (split("\n", $innerBuffer)) {
    print "BUFFER (inner): $no; #>>$line<\n";
    $no++;
    }
}

sub outerAction {
    print STDERR "OUTER before call\n"; # to outerbuffer
    handleInner();
    print STDERR "OUTER past call\n"; # to outerbuffer
}
sub handleOuter {
    print STDERR "OUTER BEFORE CAPTURE\n";
    
    my ($outerBuffer, @resuts) = capture_stderr {outerAction();};
    
    print STDERR "OUTER PAST RESTORE\n";
    chomp $outerBuffer;
    my $no=1;
    foreach my $line (split("\n", $outerBuffer)) {
    print "BUFFER (outer): $no; #>>$line<\n";
    $no++;
    }
}

handleInner();
print "################################# \n";
handleOuter();

[download]
Produces this output which shows that the outer redirect continues when the inner redirect is done. 
INNER before capture
INNER after restore
INNER past restore
BUFFER (inner): 1; #>>FIRST CAPTURE<
################################# 
OUTER BEFORE CAPTURE
BUFFER (inner): 1; #>>FIRST CAPTURE<
OUTER PAST RESTORE
BUFFER (outer): 1; #>>OUTER before call<
BUFFER (outer): 2; #>>INNER before capture<
BUFFER (outer): 3; #>>INNER past restore<
BUFFER (outer): 4; #>>OUTER past call<

[download]
BTW: Account creation is really a pain here. And only 10 letters for passwords?

In reply to Re^2: Nested redirect for STDERR to a string buffer within a perl program by Anonymous Monk
in thread Nested redirect for STDERR to a string buffer within a perl program by Anonymous Monk

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