${(I:expression:)…}: Pattern match selector

(I:expression:) is only useful with parameter expansion operators ${.../...}, ${(S)...#...}, ${(S)...%...}. Expression is a arithmetic expression to define the first match, where the pattern matching or string replacement should start.

${(I:expression:).../...}

${I:expression:...//...}

Defines the starting position of the replacement.

${(SI:expression:)...#...}

${(SI:expression:)...##...}

Match counted from the start of the string.

${(SI:expression:)...%...}

${(SI:expression:)...%%...}

Match counted from the end of the string.

Links

• Zsh manual on parameter expansion flags