There's no bug here: "expr E" exits with status 1 if E evaluates to 0,
and expressions like "0 : '\([0-9]\)$'" do evaluate to 0.
- bug#24800: expr 8.25 seems to treat 0 in character class in... Glenn Morris
- bug#24800: expr 8.25 seems to treat 0 in character cla... Paul Eggert
- bug#24800: expr 8.25 seems to treat 0 in character... Pádraig Brady
- bug#24800: expr 8.25 seems to treat 0 in character... Assaf Gordon
