...
my $obj_temp = "";
   $obj_temp = $objImageMagick->Read("dir/$filename");
   "$obj_temp" if "$obj_temp";# print the error message
   $obj_temp =~ /(\d+)/;
   warn "Error Number: ".$1." Number of images read: ".0+$obj_temp;

##</code><code>##

Use of uninitialized value $1 in concatenation (.) or string at ...
Argument "Error Number:  Number of images read: 0" isn't numeric in addition (+) at 1 at ...
Warning: something's wrong at ...