A co-worker in my shop is starting to appreciate the smell of Perl. We had a discussion about recursive function calls in general and he went off writing a small test script to get familiar with the concept.

I told him to use strict and warnings or die. He didn't want to die just yet, so he obeyed. Then he came to me asking for an explanation to something I hadn't foreseen:

#!/usr/bin/perl -w
use strict;
my $line;

open (IN, "<david2");
open (OUT, ">temp");

while ($line = <IN>) {
    process($line);
}
exit;

sub process {
    my $str=shift;
#    my $rest;

   ($a, $b, $rest) = split(/\s+/,$str,3);
    if (defined($a)){
        print OUT "$a\t";
    }
    if (defined($b)){
        print OUT "$b\n";
    }
   if (!defined($rest)){
        return (0);
   }
    process($rest);
}
[download]

If he runs the above script, perl will complain that $rest requires explicit package name etc. Fine. Removing the comment before my $rest will make perl happy. Fine again.

The question is: Why doesn't perl require explicit package names for $a and $b?

We have tried the script both under Solaris and Win-32 Active State, Perl 5.6 in both cases. Same result.

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Everything will go worng!