---
name: "Perl::Critic::Policy::ValuesAndExpressions::NotWithCompare"
section: "3pm"
platform: "linux"
package: "libperl-critic-pulp-perl"
version: "99-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/Perl::Critic::Policy::ValuesAndExpressions::NotWithCompare"
---

# Perl::Critic::Policy::ValuesAndExpressions::NotWithCompare(3pm)

logical not used with compare

## NAME

Perl::Critic::Policy::ValuesAndExpressions::NotWithCompare - logical not used with compare

## DESCRIPTION

This policy is part of the `"Perl::Critic::Pulp"` add-on.  It picks up some cases of logical not `"!"` used with a comparison, like

```
    ! $x =~ /^[123]/  # bad
    ! $x + $y >= $z   # bad
```

In each case precedence means Perl parses this as `"(!$x)"`, like

```
    (! $x) =~ /^[123]/
    (! $x) + $y >= $z
```

rather than a negated comparison.  Usually this is a mistake, so this policy is under the "bugs" theme (see "POLICY THEMES" in Perl::Critic).

As a special case, `"!"` on both sides of `"=="` or `"!="` is allowed, since it's quite a good way to compare booleans.

```
    !$x == !$y   # ok
    !$x != !$y   # ok
```

## LIMITATIONS

User functions called without parentheses are assumed to be usual varargs style.  But a prototype may mean that's not the case, letting a bad `"!"`-with-compare expression to go undetected.

```
    ! userfunc $x == 123   # indeterminate
    # without prototype would be ok:   ! (userfunc ($x==123))
    # with ($) prototype would be bad: (! userfunc($x)) == 123
```

Perl builtins with no args, and constant subs created with `"use constant"` or `"sub FOO () {...}"` in the file under test are recognised.  Hopefully anything else too weird is rare.

```
    ! time == 1   # bad
    use constant FIVE => 5;
    ! FIVE < 1    # bad
    sub name () { "foo" }
    ! name =~ /bar/    # bad
```

## SEE ALSO

Perl::Critic::Pulp, Perl::Critic

## HOME PAGE

http://user42.tuxfamily.org/perl-critic-pulp/index.html

## COPYRIGHT

Copyright 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2019, 2021 Kevin Ryde

Perl-Critic-Pulp is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version.

Perl-Critic-Pulp is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with Perl-Critic-Pulp.  If not, see \<http://www.gnu.org/licenses/\>.