And you can write your own function that takes an implicit $_ using the (_) prototype.

My favourite use for $_ is when defining a function that accepts a coderef. Example

# This is a fairly useless function which is basically
# just a copy of grep which enforces numeric context
# on the list items...
#
sub filter_nums (&@)
{
  my $coderef = shift;
  return
    grep { $coderef->() }
    map  { 0 + $_ }
    @_
}

my @even = filter_nums { not($_ % 2) } qw(1 2 3 4 potato);
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