my %x = (field => $F[$_ - 1], value => $F[$_]);

##</code><code>##

my %x = (field => $F[(--$_)++], value => $F[$_]);

##</code><code>##

my %x = (field => $F[--$_++], value => $F[$_]);

##</code><code>##

my %x = (field => $F[--$_], value => $F[++$_]);

##</code><code>##

my %x = (field => $F[~-$_], value => $F[$_]);