>perl -Mstrict -le"{ package PKG; $foo=1; }"
Global symbol "$foo" requires explicit package name at -e line 1.
Execution of -e aborted due to compilation errors.

>perl -Mstrict -le"{ package PKG; no strict 'vars'; $foo=1; } print for grep /foo/, keys %main::"

>perl -Mstrict -le"{ package PKG; our $foo=1; } print for grep /foo/, keys %main::"

>perl -Mstrict -le"{ package PKG; no strict 'vars'; $foo=1; } print for grep /foo/, keys %PKG::"
foo

>perl -Mstrict -le"{ package PKG; our $foo=1; } print for grep /foo/, keys %PKG::"
foo