G'day leszekdubiel,

"open() - Duping filehandles" explains how you can do this. Here's some example code (stderr_test.pl):

#!/usr/bin/env perl

use strict;
use warnings;
use autodie;

use Spreadsheet::ParseXLSX;

my $original_stderr;

eval {
    open $original_stderr, '>&', \*STDERR;
    open STDERR, '>&', \*STDOUT;
    Spreadsheet::ParseXLSX->new->parse('invalid.xlsx');
    1;
}
or do {
    my $err = $@;
    print $err;
};

open STDERR, '>&', $original_stderr;
warn "Now back to normal STDERR\n";
[download]

I set up a clean directory to show how this works.

ken@titan ~/tmp/pm_11146229
$ ls -l
total 1
-rw-r--r-- 1 ken None   0 Aug 19 17:09 invalid.xlsx
-rwxr-xr-x 1 ken None 380 Aug 19 18:10 stderr_test.pl

ken@titan ~/tmp/pm_11146229
$ ./stderr_test.pl > stdout.out 2> stderr.out

ken@titan ~/tmp/pm_11146229
$ ls -l
total 6
-rw-r--r-- 1 ken None    0 Aug 19 17:09 invalid.xlsx
-rw-r--r-- 1 ken None   26 Aug 19 18:11 stderr.out
-rwxr-xr-x 1 ken None  380 Aug 19 18:10 stderr_test.pl
-rw-r--r-- 1 ken None 1105 Aug 19 18:11 stdout.out

ken@titan ~/tmp/pm_11146229
$ cat stdout.out
format error: file is too short
 at /home/ken/perl5/perlbrew/perls/perl-5.36.0/lib/site_perl/5.36.0/Ar
+chive/Zip/Archive.pm line 1031.
        Archive::Zip::Archive::_findEndOfCentralDirectory(Archive::Zip
+::Archive=HASH(0x8000b79b0), IO::File=GLOB(0x800099368)) called at /h
+ome/ken/perl5/perlbrew/perls/perl-5.36.0/lib/site_perl/5.36.0/Archive
+/Zip/Archive.pm line 761
        Archive::Zip::Archive::readFromFileHandle(Archive::Zip::Archiv
+e=HASH(0x8000b79b0), IO::File=GLOB(0x800099368), "invalid.xlsx") call
+ed at /home/ken/perl5/perlbrew/perls/perl-5.36.0/lib/site_perl/5.36.0
+/Archive/Zip/Archive.pm line 729
        Archive::Zip::Archive::read(Archive::Zip::Archive=HASH(0x8000b
+79b0), "invalid.xlsx") called at /home/ken/perl5/perlbrew/perls/perl-
+5.36.0/lib/site_perl/5.36.0/Spreadsheet/ParseXLSX.pm line 63
        Spreadsheet::ParseXLSX::parse(Spreadsheet::ParseXLSX=HASH(0x80
+17a9b88), "invalid.xlsx") called at ./stderr_test.pl line 14
        eval {...} called at ./stderr_test.pl line 17
Can't open file 'invalid.xlsx' as a zip file at /home/ken/perl5/perlbr
+ew/perls/perl-5.36.0/lib/site_perl/5.36.0/Spreadsheet/ParseXLSX.pm li
+ne 63.

ken@titan ~/tmp/pm_11146229
$ cat stderr.out
Now back to normal STDERR

ken@titan ~/tmp/pm_11146229
$
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