This mistake is not caught by warnings,

Sure it is

$ perl -Mstrict -Mwarnings -le " our $shy => (); "

$ perl -Mstrict -Mwarnings -le " our $shy => (0); "

$ perl -Mstrict -Mwarnings -le " our $shy => (1); "

$ perl -Mstrict -Mwarnings -le " our $shy => (2); "
Useless use of a constant (2) in void context at -e line 1.

$ perl -Mstrict -Mwarnings -le " our $shy => []; "
Useless use of anonymous list ([]) in void context at -e line 1.

$ perl -Mstrict -Mwarnings -le " our $shy => {}; "
Useless use of anonymous hash ({}) in void context at -e line 1.

$ perl -Mstrict -Mwarnings -le " our $shy => q{}; "
Useless use of a constant ("") in void context at -e line 1.
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