{("foo","bar")}

##</code><code>##

perl -we "{('foo','bar')}"
Useless use of a constant in void context at -e line 1.
Useless use of a constant in void context at -e line 1.

##</code><code>##

perl -we "+{(foo => 'bar')}"
Useless use of single ref constructor in void context at -e line 1.

##</code><code>##

perl -we "print +{(foo => 'bar')}->{foo}"
bar