This simple program illustrates the problem:

#!/usr/bin/perl

sub foo
{
    while (@_) { $_ = shift; $params->{$_} = shift; }
    print "$_: $params->{$_}\n", for keys %$params;
}

$_ = shift @ARGV || "world";

foo ( hello => $_ );
[download]

The line in question is the last one. As it is, the output is "hello: hello". But if I put the $_ in quotes:

foo ( hello => "$_" );
[download]

You get the expected behavior. why?

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