$ perl -wle 'print $fh'
Name "main::fh" used only once: possible typo at -e line 1.
Use of uninitialized value in print at -e line 1.

$ perl -wle 'print $fh $bar'
Name "main::bar" used only once: possible typo at -e line 1.
Name "main::fh" used only once: possible typo at -e line 1.
Can't use an undefined value as a symbol reference at -e line 1.