I'm not sure about what error you are trying to catch, but you just may want

my $pid = open3( $wtr, $rdr, $err, $httpd, '-v' ) or die " spawning bi
+nary failed $!\n ";
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or even

my $pid = open3( $wtr, $rdr, $err, $httpd, '-v' );
if ( $pid ){ print "success\n"}
   else {print "spawning failure $!\n"; }
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