Fair enough, but your snippet also doesn't crash on my machine for exactly the same reasons:

>perl # 5.8.4
use strict;
use warnings;
my $x="";
foo( substr($x,2,1) ); # crashes here
print "Alive!\n"; # not reached
sub foo {}
^Z
substr outside of string at - line 4.

>c:\perl561\bin\perl5.6.1.exe
use strict;
use warnings;
my $x="";
foo( substr($x,2,1) ); # crashes here
print "Alive!\n"; # not reached
sub foo {}
^Z
substr outside of string at - line 4.
[download]

Okay, I'm confused... is that your entire output? Was the word "Alive" in there somewhere?

It should print "Alive!" if the code doesn't crash. I don't see that in your output. If that's your entire output, then you get what I do: a crash on the substr() call. Similarly, you'll get the same kind of crash if you assign to substr(): that is, treat it like an Lvalue.

My guess is that because @_ can be assigned to, substr() behaves like an Lvalue when passed as a subroutine argument. If that's true, it's odd enough to be an oddity. :-)
--
Ytrew

Yep! That's the entire output. I've added a couple of print $]; statements, one in an END{} block, to these to show that I get some output, which means that STDOUT must be being flushed, which I assume is a clean-up time operation:

P:\test>perl -l
END{ print $] }
print $];
use strict;
use warnings;
my $x="";
foo( substr($x,2,1) ); # crashes here
print "Alive!\n"; # not reached
sub foo {}
^Z
5.008004
substr outside of string at - line 6.
5.008004

P:\test>c:\perl561\bin\perl5.6.1.exe -l
END{ print $] }
print $];
use strict;
use warnings;
my $x="";
foo( substr($x,2,1) ); # crashes here
print "Alive!\n"; # not reached
sub foo {}
^Z
5.006001
substr outside of string at - line 6.
5.006001

P:\test>
[download]

However, if I remove the subcall from the picture:

P:\test>perl
use strict;
use warnings;
my $x="";
print substr($x,2,1); # crashes here
print "Alive!\n"; # not reached
^Z
substr outside of string at - line 4.
Use of uninitialized value in print at - line 4.
Alive!

P:\test>c:\perl561\bin\perl5.6.1.exe
use strict;
use warnings;
my $x="";
print substr($x,2,1); # crashes here
print "Alive!\n"; # not reached
^Z
substr outside of string at - line 4.
Use of uninitialized value in print at - line 4.
Alive!

P:\test>
[download]

Which indicates that the execution path is being truncated or short ciruited when the subcall is in place, but no crash, just a silent move to the END{} of the program--which isn't very freindly.

Seems to be a Win32 thing, and one probably worth reporting even though I cannot see how to provide any sort of indication of where the problem might occur?

---

Examine what is said, not who speaks.

Silence betokens consent.

Love the truth but pardon error.