こんなの use strict; use warnings; use Data::Dumper; sub nreturn { return } sub undefreturn { return undef } sub nop {} print Dumper({ a => nreturn, b => nreturn, }); print Dumper({ a => undefreturn, b => undefreturn, }); print Dumper({ a => nop, b => nop, }); 答え $VAR1 = { 'a' => 'b' }; $VAR1 = { 'a' => undef, 'b' => undef }; $VAR1 = { 'a' => 'b' };