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caller

Perl 5 version 10.0 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 10
    4. $wantarray, $evaltext, $is_require, $hints, $bitmask, $hinthash)
    5. = caller($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.

    $hinthash is a reference to a hash containing the value of %^H when the caller was compiled, or undef if %^H was empty. Do not modify the values of this hash, as they are the actual values stored in the optree.

    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.