use feature qw(say state);

my @widths = (2, 6, 5, 7);
my @partitions = map { state $c = 0; [$c, $c += $_] } @widths;

say '[', join(', ', @$_), ']' for @partitions;

##</code><code>##

[0, 2]
[2, 8]
[8, 13]
[13, 20]

##</code><code>##

[2, 2]
[8, 8]
[13, 13]
[20, 20]