D:\Development>perl -Mstrict -wle "my $foo=1 if 0; print defined($foo) ? $foo : 'undef'"
undef

D:\Development>perl -Mstrict -wle "if ( 0 ) { my $foo=1 }  print defined($foo) ? $foo : 'undef'"
Global symbol "$foo" requires explicit package name at -e line 1.
Global symbol "$foo" requires explicit package name at -e line 1.
Execution of -e aborted due to compilation errors.