expr: '^' should act as a special character at the start of a subexpression

[frendsick]

^ acts as a special character only at the beginning of the regular expression or subexpression (that is, after ( or |).

Reference: https://www.gnu.org/software/sed/manual/html_node/BRE-syntax.html

Examples

• expr b : 'a\|^b'
  • Expected: "1"
  • Got: "0"
• expr ab : '\(^a\)b'
  • Expected: "a"
  • Got: ""