$ perl -le "  $f = \*STDOUT; w $f, 6; "
Can't locate object method "w" via package "IO::File" at -e line 1.

$ perl -le "  sub w { warn @_ }  $f = \*STDOUT; w $f, 6; "
GLOB(0x99a674)6 at -e line 1.

$ perl -le "  $f = \*STDOUT; w $f, 6; sub w { warn @_; } "
Can't locate object method "w" via package "IO::File" at -e line 1.

$ perl -le "  sub w; $f = \*STDOUT; w $f, 6; sub w { warn @_; } "
GLOB(0x99a514)6 at -e line 1.