in reply to Re^2: Returning and passing data to and from subroutines
in thread Returning and passing data to and from subroutines

If you call a sub with a single scalar, it's the same as calling it with a 1-element list. @_ will contain the one scalar, and you can get it with shift. If you want to call a sub with multiple arrays or hashes and not have them flattened, you need to use references, and you probably want to look at something like perlreftut. If you call a sub with a single array and you want to get all the elements out at once, you can use: 

my @args=@_; # or my %args=@_ if you know it's going to be a hash

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or 
my ($arg1, $arg2, $arg3) = @_; # faster than (shift,shift,shift)

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the second form there assumes you know how many arguments you're going to get, or don't care if some of them come back undef.

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Re^4: Returning and passing data to and from subroutines
by vendion (Scribe) on Jul 21, 2010 at 04:05 UTC

    Thanks, the reason I ask is because some how I have done something wrong. When at the programs menu if I were to input lets say "10" it some how returns as a 1 then it fails the test causing my display_menu_error sub to be executed with this error "ERROR: illegal option: 1 selected" some where along the line the 10 I give the program is changed: 

    db_connect();    #Connect to the database if needed
while ( display_menu(), ( my $option = <> ) ) {
 print '$option before processing input: ' . $option # returns 10
 $option = process_input($option);
 print '$option after processing input: ' . $option # returns 1
 if ( ( $option !~ m{/^\d+$/}xms ) or ( $option <= 0 ) or ( $option > 
+10 ) ) {
  display_menu_error("ERROR: illegal option: $option selected\n");
  next;
 }
 print_form()     if $option == 1;
 print_edit()     if $option == 2;
 db_remove()      if $option == 3;
 db_fetch()       if $option == 4;
 print_all()      if $option == 5;
 print_report()   if $option == 6;
 db_check()       if $option == 7;
 leave_comment()  if $option == 8;
 leave_donation() if $option == 9;

 if ( $option == 10 ) {
  $dbh->disconnect;
  print "Quitter...\n";
  exit 0;
 }
}
...
sub process_input {

# takes in information and loops through testing the input for valid a
+lphanumeric characters.
 my @data = @_;
 for (@data) {
  chomp;
  s/^\s*//; # Have tried commenting out no change
  s/\s*$//; # Still somehow returns incorrect values
 }
 return @data;
}

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    I just can't see why it would be doing that to me like that
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[d/l]

      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

      [download]
      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.

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