Looks like not the OP's (i.e. davidfilmer) case, but, sadly, libtiff shipped with Strawberry Perl generates warnings as ugly pop-up GUI modal boxes, requiring user interaction to dispose. Therefore, without recompilation, the solution with Capture::Tiny won't work.

On the other hand, libtiff provides a TIFFSetWarningHandler function just for customizing error reporting. It is not exposed by the Perl wrapper, but adding that feature shouldn't be too difficult.

Ah, then I can do it:

use strict;
use warnings;
use Graphics::TIFF;

my $fn = 'TIFF01.TIF';  # a file known to generate 
                        # a warning (as shown below)

DummyTiffLogger::init();

Graphics::TIFF-> Open( $fn, 'r' ) 
    for 1..5;

package DummyTiffLogger {

sub logMessage {
    my $s = shift;
    printf "message logged: <%s>\n", $s
}

use Inline C => Config => LIBS => '-ltiff';
use Inline C => <<'END_OF_C';

#define BUFSIZE 1024

void _log(char* m, char* fmt, va_list ap) {
    char* buf;
    int len;
    SV* sv;
    
    Newxz(buf, BUFSIZE, char);
    len = vsprintf(buf, fmt, ap);
    Renew(buf, len + 1, char);
    sv = newSV(0);
    sv_usepvn_flags(sv, buf, len, SV_SMAGIC | SV_HAS_TRAILING_NUL);

    dSP;
    ENTER;
    SAVETMPS;
    PUSHMARK(SP);
    XPUSHs(sv_2mortal(sv));
    PUTBACK;

    call_pv("DummyTiffLogger::logMessage", G_DISCARD);

    FREETMPS;
    LEAVE;
}

void init() { TIFFSetWarningHandler(&_log); }

END_OF_C
}           # package

__END__

message logged: <Unknown field with tag 32781 (0x800d) encountered>
message logged: <Unknown field with tag 32781 (0x800d) encountered>
message logged: <Unknown field with tag 32781 (0x800d) encountered>
message logged: <Unknown field with tag 32781 (0x800d) encountered>
message logged: <Unknown field with tag 32781 (0x800d) encountered>

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In reply to Re^3: How to capture (intercept) output (warnings) of a module by vr
in thread How to capture (intercept) output (warnings) of a module by davidfilmer

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