$ perl -wE 'sub f {state (my $x); say ++$x} f; f;'
1
1
$ perl -wE 'sub f {my (state $x); say ++$x} f; f;'
1
2
$ perl -wE 'sub f {state my $x; say ++$x} f; f;'
No such class my at -e line 1, near "{state my"
Execution of -e aborted due to compilation errors.