Re^6: regex syntax and idomatic Perl

So ... $_ in the for loop, and $y are references

Not exactly, $_ is an alias to the elements being looped over, not a reference (which would need to be dereferenced), see the first few paragraphs of Foreach Loops. Some more fun with aliases, note how the magic substr lvalue remembers its bounds in the string:

our ($x,$y) = "Hello, World!";
*y = \substr $x, 7, 5;  # alias via glob

$y = "substring";
print "<$x>\n";  # prints <Hello, substring!>

$y = "Perl";
print "<$x>\n";  # prints <Hello, Perl!>

$x = "Magic, cool stuff!";
print "<$y>\n";  # prints <cool>
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Re^7: regex syntax and idomatic Perl by cbeckley (Curate) on Mar 23, 2017 at 14:44 UTC
Ah, I think I see (again). So, in the for loop, $_ is an alias to the same memory location as the element in the list being looped over. If that memory location is occupied by something that is semantically an lvalue, then $_ behaves as if it were a C pointer, which is to say, behaves just like the thing it's pointing to. If the memory location is not an lvalue, then $_ does not behave like a C pointer, but still behaves like the thing it's pointing to. Is that right? I have to stop trying to understand the mechanics of Perl in terms of C. <Insert Yoda quote here.> So, $_ is imbued with the semantic context of the thing that occupies the memory location to which it points. Still thinking in C, clearly ...	[reply]

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Re^7: regex syntax and idomatic Perl
by cbeckley (Curate) on Mar 23, 2017 at 14:44 UTC

Ah, I think I see (again). So, in the for loop, $_ is an alias to the same memory location as the element in the list being looped over. If that memory location is occupied by something that is semantically an lvalue, then $_ behaves as if it were a C pointer, which is to say, behaves just like the thing it's pointing to. If the memory location is not an lvalue, then $_ does not behave like a C pointer, but still behaves like the thing it's pointing to.
Is that right?

I have to stop trying to understand the mechanics of Perl in terms of C.
<Insert Yoda quote here.>
So, $_ is imbued with the semantic context of the thing that occupies the memory location to which it points. Still thinking in C, clearly ...

[reply]