Hi
I have been reading the camel book; it's really fantastic
(and funny), but I still didn't understand some topics.
One thing that's not so clear is about constants made with
typeglobs and references; that's in page 295 of 3rd Ed.
I have made the following program to test them:
#!/usr/bin/perl -w
use strict;
our $PI;
$PI = \3.1415926535;
print "(1) $PI\n";
# prints SCALAR(0x8101f64)
$PI = 7;
print "(2) $PI\n";
# prints 7
*PI = \4.31415926;
print "(3) $PI\n";
# prints 4.31415926
$PI = \5.31419526;
# error: Modification of a read-only value attempted at ./m2 line 18.
print "(4) $PI\n";
And now the questions:
Question 1) Ignoring the different constant values,
Is the first and the third attributions equivalent?
It seems that not, but then, why?
I thought that when I wrote
*PI = \value
I was giving the scalar $PI the value "reference to a value",
and not the value itself (that is what's being printed)!?
Question 2) Why cannot we make the 4th attribution? What is
making the scalar $PI a read-only? It cannot be the
previous reference, because we also set it to a reference on the
first attribution, but we could change it on the second...
Thanks in advance and for a long time
Silvio Santana
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