warn "1: $!\n"; 
   my $compressed_size = -s $file; 
   warn "1: $!\n"; 
   open(my $sd_fh, "<$file") || die "bla: $!"; 
   warn "1: $!\n"; 
   warn "sd_fh: $sd_fh\n"; 
   if($!) { warn "couldn't open image, skipping: $file: $!\n"; next; };

$ perl foo.pl sd.32497.sd 
1: 
1: 
1: Inappropriate ioctl for device
sd_fh: GLOB(0x604290)
couldn't open image, skipping: sd.32497.sd: Inappropriate ioctl for device