$ perl -Mstrict -e 'print $a; die'
Name "main::a" used only once: possible typo at -e line 1.
Use of uninitialized value in print at -e line 1.
Died at -e line 1.

$ perl -Mstrict -e 'print $abc; die'    ## die not reached
Global symbol "$abc" requires explicit package name at -e line 1.
Execution of -e aborted due to compilation errors.