To get the exit code from system() you must decode $?. From perldoc -f system:

                   if ($? == -1) {
                       print "failed to execute: $!\n";
                   }
                   elsif ($? & 127) {
                       printf "child died with signal %d, %s coredump\
+n",
                           ($? & 127),  ($? & 128) ? ’with’ : ’without
+’;
                   }
                   else {
                       printf "child exited with value %d\n", $? >> 8;
                   }
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In your case that means scp returned with exit code 1. According to the scp manpage that means it encountered an error, although it doesn't tell you what kind.

-sam