Perl::Critic::Policy::BuiltinFunctions::ProhibitUselessTopic - Don't pass $_ to built-in functions that assume it, or to most filetest operators.

NAME AFFILIATION DESCRIPTION Topic unnecessary for certain Perl built−in functions Topic unnecessary for most filetest operators KNOWN BUGS CONFIGURATION AUTHOR COPYRIGHT

NAME

Perl::Critic::Policy::BuiltinFunctions::ProhibitUselessTopic − Don't pass $_ to built−in functions that assume it, or to most filetest operators.

AFFILIATION

This Policy is part of the Perl::Critic distribution.

DESCRIPTION

There are a number of places where $_, or "the topic" variable, is unnecessary.

Topic unnecessary for certain Perl built−in functions

Many Perl built−in functions will operate on $_ if no argument is passed. For example, the "length" function will operate on $_ by default. This snippet:

for ( @list ) {
if ( length( $_ ) == 4 ) { ...

is more idiomatically written as:

for ( @list ) {
if ( length == 4 ) { ...

In the case of the "split" function, the second argument is the one that defaults to $_. This snippet:

for ( @list ) {
my @args = split /\t/, $_;

is better written as:

for ( @list ) {
my @args = split /\t/;

There is one built−in that this policy does not check for: "reverse" called with $_.

The "reverse" function only operates on $_ if called in scalar context. Therefore:

for ( @list ) {
my $backwards = reverse $_;

is better written as:

for ( @list ) {
my $backwards = reverse;

However, the distinction for scalar vs. list context on "reverse" is not yet working. See KNOWN BUGS below.

Topic unnecessary for most filetest operators

Another place that $_ is unnecessary is with a filetest operator.

# These are identical.
my $size = −s $_;
my $size = −s;
# These are identical.
if ( −r $_ ) { ...
if ( −r ) { ...

The exception is after the "−t" filetest operator, which instead of defaulting to $_ defaults to "STDIN".

# These are NOT identical.
if ( −t $_ ) { ...
if ( −t ) { ... # Checks STDIN, not $_