$ perl -le '
$str = q{yands};
$str = join q{}, ( split m{}, $str )[ -1, 1 .. length( $str ) - 2, 0 ];
print $str;'
sandy
$

##</code><code>##

$ perl -le '
$str = q{yands};
substr( $str, 0, 1 ) = substr $str, length( $str ) - 1, 1, substr $str, 0, 1;
print $str;'
sandy
$