That looks a lot like the code I wrote in Re: Converting from string to SCALAR when using strict "refs". If I assume that what I learned about the problem back then still applies today, then I think you're looking for a way to tell if setting $processor failed in some way.

One way is to check $?, and that will tell you the exit status of the program you ran in backticks. I suspect you don't care about that, however, if the program gave you bogus output. What you really want is to check that you got a number from it.

To check that it gave you a number, like you want, look at ${$processor}. You could use Scalar::Util::looks_like_number, or you could match against a simple regular expression like so:

my $processor = \( 0+ `blah` );
if ( ${$processor} !~ m{ \A \d+ \z }xms ) {
    die 'oh noes';
}
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If that doesn't do what you want, you'll have to explain better what you're looking for.

Use 'perldoc -f -x' to get to the manual page of the filetest operators. To check if for example a file is executable, you would use if (-x $file) { ... }

To check if a file is corrupted there is no easy or generally usable way. If the file is a perl script you could try to check it with 'perl -c'

also, how can I test wether the value returned by the script is numeric or non-numeric?

How do I determine whether a scalar is a number/whole/integer/float?

That depends on whether by numeric you mean a simple integer like 12 or a number like -12.15 or even 12E25. You might check that with a regex, similar to what kyle already posted

chomp($processor); # removes \n 

# would check for whole numbers like 1, 12, 389
if (! $processor || $processor !~ /^\d+$/){

#would check for numbers with optional decimal point and + or minus si
+gn
if (! $processor || $processor !~ /^(+|-)?\d+(\.\d*)?$/){
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There is a cpan module that has all kinds of regexes predefined (don't rememer the name atm), if you want to check for more complex numbers, that module would be a good idea

UPDATE: Note that in the example code you posted above you have a pointer to the result in $processor and not the result itself. If you just want the result of the ccc.ksh execution in $processor, better remove the \ in front of the left paren