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
die. The author of Perl has never felt the need to use this form of
goto (in Perl, that is--C is another matter).
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];
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.