[oak perl] The mysterious "undef"

[dbkliv]

On Fri, 18 Mar 2005 12:55:46 -0500, Sandy Santra <santranyc at yahoo.com> wrote:
> For this, doesn't the "my" have to be outside the loop?
> 
> When I run:
> 
> use strict;
> sub test {
>     my ( $x, $y, $z ) = @_;
> }
> test(1,0);
> print "$x\n";
> print "$y\n";
> print "$z\n";
> print "x is undef\n" if not defined $x;
> print "y is undef\n" if not defined $y;
> print "z is undef\n" if not defined $z;
> 
> I get compilation errors (i.e., "Global symbol "$x" requires explicit
> package name at test2 line 7").

Right - because $x, $y, and $z are scoped to test().

Convert your code to:

   #!/usr/bin/perl

   use strict;
   use warnings;

   sub test {
     my ( $x, $y, $z ) = @_;
     print "$x\n";
     print "$y\n";
     print "$z\n";
     print "x is undef\n" if not defined $x;
     print "y is undef\n" if not defined $y;
     print "z is undef\n" if not defined $z;
   }

  test(1,0);
  __END__
  1
  0
  Use of uninitialized value in concatenation (.) or string at - line 10.

  z is undef