goto - create spaghetti code
goto LABEL
goto EXPR
goto &NAME
The goto-LABEL form finds the statement labeled with
LABEL and resumes
execution there. It may not be used to go into any construct that
requires initialization, such as a subroutine or a foreach loop. It
also can't be used to go into a construct that is optimized away,
or to get out of a block or subroutine given to sort.
It can be used to go almost anywhere else within the dynamic scope,
including out of subroutines, but it's usually better to use some other
construct such as last or die. The author of Perl has never felt the
need to use this form of goto (in Perl, that is--C is another matter).
The goto-EXPR form expects a label name, whose scope will be resolved
dynamically. This allows for computed gotos per
FORTRAN, but isn't
necessarily recommended if you're optimizing for maintainability:
goto ("FOO", "BAR", "GLARCH")[$i];
The goto-&NAME form is quite different from the other forms of goto.
In fact, it isn't a goto in the normal sense at all, and doesn't have
the stigma associated with other gotos. Instead, it
substitutes a call to the named subroutine for the currently running
subroutine. This is used by AUTOLOAD subroutines that wish to load
another subroutine and then pretend that the other subroutine had been
called in the first place (except that any modifications to @_
in the current subroutine are propagated to the other subroutine.)
After the goto, not even caller will be able to tell that this
routine was called first.
NAME needn't be the name of a subroutine; it can be a scalar variable containing a code reference, or a block which evaluates to a code reference.