Well, one problem you're having is context confusion:
perl -e 'sub foo {@a=(1,2,4);return @a};
$bar=foo();
print "bar is $bar\n";'
bar is 3
If you want $option to get the _value_, instead of the number of elements in the array, you'll need to either learn about
wantarray so your sub knows how it's called, or return a scalar, or do list assignment (which looks like
($option)=process_input($option). Perl is examining @data in a scalar context in your return statement, which gives the number of elements it contains, rather than its contents, because the sub was called as the rvalue of a scalar assignment.
