long time reader first time caller....
Anyway, i'm currently upgrading some legacy scripts to perl 5.10. There's a lib we've got that for some reason decided it'd be easier if arrays started at 1, so they've gone and set $[ = 1
They've done this in a module, in an init function. The code has previously run in 5.8.8, and i'm updating everything to use perl 5.10.
my test.pm example: 
#!/usr/bin/env perl

package test;

sub Init
{
    $[ = 1;
}

sub test
{
    print "(\$[= $[) array has " . scalar @_ . " elements, last index 
+= $#_\n";
}

1;

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t1.pl: 
#!/usr/bin/env perl

use test;

test::test(1,2,3,4);

# test::Init();

test::test(1,2,3,4);

[download]
As it turned out, even without calling test::Init, the mere fact that that is in that function has somehow globally turned on that option...
in perl 5.8.8, i execute the t1.pl and get: 
# perl 5.8.8 output
./t1.pl
($[= 1) array has 4 elements, last index = 4
($[= 1) array has 4 elements, last index = 4

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and in perl 5.10 
# perl 5.10
$ ./t1.pl
($[= 0) array has 4 elements, last index = 3
($[= 0) array has 4 elements, last index = 3

[download]
regardless of whether i call Init or not. I'm not sure why this happens, and it looks like it was a bug in perl 5.8.8 that wasn't listed as resolved in perl 5.10 but is...
It drove me crazy :| hopefully this information at least helps someone if they see the same thing - i've not seen it listed anywhere as a change or as something someone has tripped over. Can anyone else confirm this or is it just me? :|

In reply to fun with $[ by rolfy

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