Question

Why is it that my code is not working after I added use strict; use warnings;? Is there a way to make it work?

Previously, the working code is:

#!/usr/bin/perl -s
print "x: $x\n";
print "y: $y\n";

The command that I ran is perl -s test.pl -x="hello" -y="world". The output is:

x: hello
y: world

However, after I added use strict; use warnings;, I got the following errors:

Variable "$x" is not imported at test.pl line 4.
Variable "$y" is not imported at test.pl line 5.
Global symbol "$x" requires explicit package name at test.pl line 4.
Global symbol "$y" requires explicit package name at test.pl line 5.
Execution of test.pl aborted due to compilation errors.

I know I need to declare my $x and my $y to fix the 3rd and 4th error. But what does the first 2 errors mean and how do I overcome it?

Answer 1

You are using a a rudimentary switch parser perl -s, which uses global variables. To make it work with use strict you need to refer to the globals: $main::x as ruakh pointed out.

But even so, lexical variables (declared with my) are preferable in just about all cases. Just do:

use strict;
use warnings;

my ($x, $y) = @ARGV;
print "x: $x\n";
print "y: $y\n";

And use with:

perl test.pl hello world

For a more detailed and switch like handling, check out the Getopt::Long module.