Programming Perl, 4th Edition

The goto Operator

Although not for the faint of heart (nor for the pure of heart), Perl does support a goto operator. There are three forms: goto LABEL, goto EXPR, and goto &NAME.

The goto LABEL form finds the statement labelled with LABEL and resumes execution there. It can’t be used to jump into any construct that requires initialization, such as a subroutine or a foreach loop. It also can’t be used to jump into a construct that has been optimized away (see Chapter 16). It can be used to go almost anywhere else within the current block or any block in your dynamic scope (that is, a block you were called from). You can even goto out of subroutines, but it’s usually better to use some other construct. The author of Perl has never felt the need to use the labelled form of goto in Perl (except to test that it works).

The goto EXPR form is just a generalization of goto LABEL. It expects the expression to produce a label name, whose location obviously has to be resolved dynamically by the interpreter. This allows for computed gotos per FORTRAN, but isn’t necessarily recommended if you’re optimizing for maintainability:

goto(("FOO", "BAR", "GLARCH")[$i]);         # hope 0 <= i < 3

@loop_label = qw/FOO BAR GLARCH/;
goto $loop_label[rand @loop_label];         # random teleport

In almost all cases like this, it’s usually a far, far better idea to use the structured control-flow mechanisms of next, last, or redo instead of resorting to a goto. For certain applications, a hash of references to functions or the ...