Re: [MacPerl] FNG

[rjk@linguist.dartmouth.edu (Ronald J. Kimball)]

Chris Nandor wrote:
> 
> If $w contained the null string (or undef), it would not have printed
> 2**32-1 for ~$_.  But if it contained 0, then it would not have printed
> nothing for $_.  0 clearly is not returned.  The null string clearly was
> not returned.  My best guess is that it is some other kind of null, a null
> number.
> 

Why guess when you can be certain?  :-)
(This requires a debugging build.)

~> cat > tmp.pl
/a/;
~> perl -Dctls tmp.pl

EXECUTING...

    =>  
(tmp.pl:0) enter
Entering block 0, type BLOCK
    =>  
(tmp.pl:0) nextstate
    =>  
(tmp.pl:1) match
    =>  SV_NO  
(tmp.pl:1) leave
Leaving block 0, type BLOCK
~> 


As you can see, the failed match puts the special scalar SV_NO on the
stack.  Presumably, SV_NO comprises an integer value of 0 and a string
value of ''.  This explains the output of Chris's program with regards to
$w.

There is also an SV_YES, which is returned by print.

Ronald

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