Programming Perl, 4th Edition

state

state EXPR
state TYPE EXPR
state EXPR : ATTRS
state TYPE EXPR : ATTRS

The state declarator introduces a lexically scoped variable, just as my does. However, the contents of state variables persist across calls to the same routine; such variables can only be initialized once the first time the scope is entered and will never be reinitialized, unlike lexical variables, which are reinitialized each time their enclosing scope is entered.

When a closure is cloned, it is considered a new subroutine, so any state variables will be initialized in the new clone on first call. State variables are not static in the sense a C programmer would think of it, unless the routine itself is static.

State variables are enabled only when the use feature "state" pragma is in effect. See the section feature in Chapter 29. Only initialization of scalar state variables is fully supported at this time, though you may always use a scalar reference to an array or hash.