Daftar Isi

• 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, ifwe're in a subroutine or eval or require) and the undefined valueotherwise. In list context, returns

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

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

   #  0 1  2  3 4
   
   ($package, $filename, $line, $subroutine, $hasargs,
   
   
   #  5  6  7 8   9 10
   
   $wantarray, $evaltext, $is_require, $hints, $bitmask, $hinthash)
   
   = caller($i);
   

  Here $subroutine may be (eval) if the frame is not a subroutinecall, 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 arequire or use statement, $evaltext contains the text of theeval EXPR statement. In particular, for an eval BLOCK statement,$subroutine is (eval), but $evaltext is undefined. (Note also thateach use statement creates a require frame inside an eval EXPRframe.) $subroutine may also be (unknown) if this particularsubroutine happens to have been deleted from the symbol table.$hasargs is true if a new instance of @_ was set up for the frame.$hints and $bitmask contain pragmatic hints that the caller wascompiled with. The $hints and $bitmask values are subject to changebetween versions of Perl, and are not meant for external use.

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

  Furthermore, when called from within the DB package inlist context, and with an argument, caller returns moredetailed information: it sets the list variable @DB::args to be thearguments with which the subroutine was invoked.

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

  Be aware that setting @DB::args is best effort, intended fordebugging or generating backtraces, and should not be relied upon. Inparticular, as @_ contains aliases to the caller's arguments, Perl doesnot take a copy of @_, so @DB::args will contain modifications thesubroutine makes to @_ or its contents, not the original values at calltime. @DB::args, like @_, does not hold explicit references to itselements, so under certain cases its elements may have become freed andreallocated for other variables or temporary values. Finally, a side effectof the current implementation is that the effects of shift @_ cannormally be undone (but not pop @_ or other splicing, and not if areference to @_ has been taken, and subject to the caveat about reallocatedelements), so @DB::args is actually a hybrid of the current state andinitial state of @_. Buyer beware.