---
name: index
status: documented
runtime: pp
source: src/runtime/pp/strings/search.rs
---
```{index} single: index; Perl built-in (pp runtime)
```

# index

## Synopsis

```perl
$pos = index($string, $substr);
$pos = index($string, $substr, $start);
```

## Description

Finds the first occurrence of a substring within a string.

Searches STRING for the first occurrence of SUBSTR starting at
character position START (default 0). Returns the zero-based
character position of the match, or -1 if the substring is not found.

Positions are in characters (not bytes), so this works correctly with
multi-byte UTF-8 strings. An ASCII fast path avoids the overhead of
character-index conversion when both operands are pure ASCII.

When the `OPpTARGET_MY` flag (0x10) is set, the result is stored
directly into the pad slot rather than pushed to the stack.

## See also

rindex, substr, pos