In "The Perl Review" spring 07 page 10 it states:
"With Perl 5.10 I can write my own lexical pragmas.
In fact, feature was implemented this way. The
%^H special variable lets me attach "references" to
the optree, which I can then inspect with caller.
Perl passes this information as a new item in the
return list for caller: a hash reference of pragma
settings."
Questions:
1) What is the optree and how is it useful?
2) What is the official name for %^H
3) Using caller, what is element 10 in the code below?
I looked in Programming Perl (w/out hope) and did
not find it.
($package, $filename, $line, $subr, $has_args,
$wantarray )= caller($i);
# 0 1 2 3 4 5
CODE AS BELOW:
package foomagazin;
use feature qw(say ~~);
sub import{
$^H{german} = 1 if @_ ~~ 'german';
}
sub unimport{
$^H{german} = 0 if @_ ~~ 'german';
}
sub hello_world{
my $hash = (caller(0))[10];
if( $hash->{german} ) {
say "Hallo Welt!";
}
else {
say "Hello World!";
}
}
1;
thank you
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