OK, get_cpu_used_by_other_process really is returning a reference to a scalar. That being the case, I guess you really do need to use the backslash as I suggested in Re^3: converting from string to SCALAR when using strict "refs".

my $processor = \`/aa/bin/get_pbind_cpus.ksh`;
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However, you might need to chomp that before doing anything with it because the backticks will give you a newline at the end of the value you're interested in.

chomp( $$processor );
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Then your offending line 325 can be what you had originally.

system("$os_cmd_table{$^O}{pbind} -b $$processor $$proc_id{$_} >/dev/n
+ull 2>&1") if defined $$processor;
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I hope that helps.