$ perl -E '
    use constant X => "a";
    sub Y {"b"}
    my %h = qw{a 1 b 2 X 24 Y 25};
    say for $h{X}, $h{"X"}, $h{+X}, $h{X()}, $h{(X)};
    say for $h{Y}, $h{"Y"}, $h{+Y}, $h{Y()}, $h{(Y)};
'
24
24
1
1
1
25
25
2
2
2