$ perl -wMstrict -le 'eval "%hash1=(); 1" or warn "<<$@>>"'
<<Global symbol "%hash1" requires explicit package name (did you forget to declare "my %hash1"?) at (eval 1) line 1.
>> at -e line 1.
$ perl -wMstrict -le 'my %hash1; my %hash1; print "Foo";'
"my" variable %hash1 masks earlier declaration in same scope at -e line 1.
Foo
$ perl -wMstrict -le 'my %hash1; { my %hash1; } print "Foo";'
Foo
$ perl -wMstrict -le 'my %hash1; eval "my %hash1;"; print "Foo";'
Foo