Double quotes, existing key: <!exist bar>
Not executing this time.
But there was an error:
    Can't locate object method "exist" via package "bar" (perhaps you forgot to load "bar"?) at (eval 1) line 1.

Double quotes, existing key: <!exist bar>
Not executing this time.
But there was an error:
    Can't locate object method "exist" via package "bar" (perhaps you forgot to load "bar"?) at (eval 2) line 1.

Single quotes, existing key: <!exists $hash{bar}>
Not executing this time.

Single quotes, non-existing key: <!exists $hash{baz}>
This is executed!