The effects do vary in some cases, since ++ is smarter than it looks.

use strict;
use warnings;

my $index = 'AH';
$index++;
print "++ gives $index\n";
$index += 1;
print "+= gives $index\n";
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Results in:

++ gives AI
Argument "AI" isn't numeric in addition (+) at test.pl line 7.
+= gives 1
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