Maybe the reason backticks didn't work is because you are on Unix and "." is not in your path. This works.

$ ./2.pl
Hello
$ cat 1.pl
#!/usr/bin/perl

print "Hello\n";

$ cat 2.pl
#!/usr/bin/perl

my $output = `./1.pl`;

print $output;
[download]

EDIT: Not having "." in your PATH on a Unix box also explains the -1 return code you got from system(). The shell could not find the success.pl executable in your PATH.