use strict;
use warnings;
use 5.010;

my $pat     = ':';
my $str     = 'O:K';
my $pat_ref = \$pat;
my $str_ref = \$str;
my @par     = ( $pat, $str );

my $rv = split $pat,      $str;         # OK
$rv = split $pat,      $$str_ref;    # OK
$rv = split $$pat_ref, $$str_ref;    # OK
$rv = split( $par[0], $par[1] );     # OK

# W1: Use of uninitialized value $_ in split

$rv = split @par;                      # NOK W1
$rv = split(@par);                     # NOK W1
$rv = split( @par[ 0, 1 ] );           # NOK W1
$rv = split( ( @par[ 0, 1 ] ) );       # NOK W1
$rv = split( map { $_ } @par );        # NOK W1
$rv = split( ( map { $_ } @par ) );    # NOK W1