---
name: y///
signature: 'y/SEARCHLIST/REPLACEMENTLIST/cdsr'
status: documented
categories: ["SCALARs and strings"]
---

```{index} single: y///; Perl built-in
```

*[SCALARs and strings](../perlfunc-by-category)*

# y///

Transliterate characters in a string. `y///` is a synonym for
[`tr///`](tr) — the two are identical in every respect.

The `y` spelling is provided for **sed** devotees, whose muscle memory
produces `y/abc/ABC/` rather than `tr/abc/ABC/`. Perl's parser accepts
either; the resulting op is the same. Use whichever spelling reads
better in the surrounding code — if the file already quotes a sed
script, `y///` often fits; in fresh Perl, `tr///` is more common.

## Synopsis

```perl
y/SEARCHLIST/REPLACEMENTLIST/cdsr
$var =~ y/SEARCHLIST/REPLACEMENTLIST/cdsr
y/SEARCHLIST/REPLACEMENTLIST/      # transliterates $_
```

## What you get back

Same as `tr///`:

- Without `/r`: the number of characters matched (and replaced or
  deleted), after modifying the target in place.
- With `/r`: a new string with the transliteration applied; the
  original is untouched.

## Examples

Classic sed-style uppercase transliteration on [`$_`](../perlvar):

```perl
while (<>) {
    y/a-z/A-Z/;
    print;
}
```

Counting vowels without modifying the string, using `/r` to discard
the transliterated copy:

```perl
my $vowels = ($text =~ y/aeiouAEIOU//) ;   # count in place is fine too
my $count  = () = $text =~ /[aeiouAEIOU]/g;
```

Strip everything except digits from a string (non-destructive copy
via `/r`, complement + delete):

```perl
my $digits = $phone =~ y/0-9//cdr;         # "(415) 555-1212" → "4155551212"
```

Rot13 — the textbook `y///` one-liner:

```perl
(my $coded = $plain) =~ y/A-Za-z/N-ZA-Mn-za-m/;
```

## Edge cases

See [`tr///`](tr) for the full list. Two worth repeating here:

- **No variable interpolation.** `y/$x/$y/` transliterates the literal
  characters `$`, `x` against `$`, `y` — not the contents of those
  variables. This matches `tr///` and is the single most common
  sed-to-Perl translation bug.
- **`y'...'...'` disables ranges.** With single-quote delimiters,
  `-` is literal: `y'a-z'A-Z'` transliterates only `a`, `-`, `z`
  against `A`, `-`, `Z`.

## Differences from upstream

Fully compatible with upstream Perl 5.42.

## See also

- [`tr///`](tr) — the canonical spelling; identical semantics, same
  flags (`/c`, `/d`, `/s`, `/r`), same edge cases
- [`s///`](s) — pattern-based substitution when character-by-character
  mapping is not enough
- [`lc`](lc), [`uc`](uc) — locale- and Unicode-aware case change;
  prefer these over `y/a-z/A-Z/` for anything beyond ASCII
- [`$_`](../perlvar) — the default target when no `=~` binding is given