Superstition makes me post-increment; I think it’s not slower anymore but was back in the dinosaur age.

Post-increment is necessarily slower since it requires making a copy of the scalar that pre-increment doesn't. However, Perl replaces post-increment operators in void context with pre-increment operators.

$ perl -MO=Deparse -e'$_++ for @a;'
++$_ foreach (@a);
-e syntax OK

$ perl -MO=Deparse -e'map { $_++ } @a;'
map {$_++;} @a;
-e syntax OK
[download]

BTW:

#!/usr/bin/env perl
use strict;
use warnings;
use Data::Dump;

my @original_data_set = ( 1 .. 10 );
dd \@original_data_set;

my @modified_data_set = map { $_++} @original_data_set;
dd \@original_data_set, \@modified_data_set;

__END__
karl-mac-mini:monks karl$ ./1119980.pl
[1 .. 10]
([2 .. 11], [1 .. 10])
[download]

Best regards, karl

«The Crux of the Biscuit is the Apostrophe»

So the so called "modified" set isn't really modified because its a post increment.

While being consistent and logic it's indeed surprising, and a good reason to generally prefer pre-increments.

edit

Thanks seems like I have to rethink my habit.

Cheers Rolf
_{(addicted to the Perl Programming Language and ☆☆☆☆ :)}

PS: Je suis Charlie!