$ perl -wle'use strict; map +(my $x = $_), 2; print $x'
Use of uninitialized value $x in print at -e line 1.

$ perl -wle'use strict; { map +(my $x = $_), 2; } print $x'
Global symbol "$x" requires explicit package name at -e line 1.
Execution of -e aborted due to compilation errors.