$ perl -Mstrict -Mwarnings -e 'map{ "$_" => 1 } ();'
syntax error at -e line 1, near "} ("
$ perl -Mstrict -Mwarnings -e 'map{ $_ => 1 } ();'
$ perl -Mstrict -Mwarnings -e 'my $z = "z"; map{ "$z$_" => 1 } ();'
syntax error at -e line 1, near "} ("