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caller

Perl 5 version 8.9 documentation
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caller

  • caller EXPR

  • caller

    Returns the context of the current subroutine call. In scalar context, returns the caller's package name if there is a caller, that is, if we're in a subroutine or eval or require, and the undefined value otherwise. In list context, returns

    1. # 0 1 2
    2. ($package, $filename, $line) = caller;

    With EXPR, it returns some extra information that the debugger uses to print a stack trace. The value of EXPR indicates how many call frames to go back before the current one.

    1. # 0 1 2 3 4
    2. ($package, $filename, $line, $subroutine, $hasargs,
    3. # 5 6 7 8 9
    4. $wantarray, $evaltext, $is_require, $hints, $bitmask) = caller($i);

    Here $subroutine may be (eval) if the frame is not a subroutine call, but an eval. In such a case additional elements $evaltext and $is_require are set: $is_require is true if the frame is created by a require or use statement, $evaltext contains the text of the eval EXPR statement. In particular, for an eval BLOCK statement, $subroutine is (eval) , but $evaltext is undefined. (Note also that each use statement creates a require frame inside an eval EXPR frame.) $subroutine may also be (unknown) if this particular subroutine happens to have been deleted from the symbol table. $hasargs is true if a new instance of @_ was set up for the frame. $hints and $bitmask contain pragmatic hints that the caller was compiled with. The $hints and $bitmask values are subject to change between versions of Perl, and are not meant for external use.

    Furthermore, when called from within the DB package, caller returns more detailed information: it sets the list variable @DB::args to be the arguments with which the subroutine was invoked.

    Be aware that the optimizer might have optimized call frames away before caller had a chance to get the information. That means that caller(N) might not return information about the call frame you expect it do, for N > 1 . In particular, @DB::args might have information from the previous time caller was called.