caller
eval or require, and the
undefined value otherwise. In a list context, returns
($package, $filename, $line) = caller;
With EXPR, it returns some extra information that the debugger uses to print a stack trace. The value of EXPR indicates how many call frames to go back before the current one.
($package, $filename, $line, $subroutine,
$hasargs, $wantarray, $evaltext, $is_require) = caller($i);
Here $subroutine may be "" if the frame is not a subroutine call, but the eval manpage. In such a case additional elements $evaltext and
$is_require are set: $is_require is true if the
frame is created by
the require manpage or the use manpage statement, $evaltext contains the text of
eval EXPR statement. In particular, for eval BLOCK
statement $filename is "", but $evaltext is undefined. (Note also that the use manpage statement creates a the require manpage frame inside an eval EXPR) frame.
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 that subroutine was invoked.