#!/usr/bin/perl -w

use warnings;
use strict;

sub processDir {
    my $args = shift; # note, default for shift here is @_;

    my $ret = qx($args->{script} $args->{dir});
    chomp($ret);
    print qq(Output:"$ret"\n) if $args->{verbose};
}

# Normally via environment variable
my $script = "echo -e"; 
# Normally via glob and processing in this script
my @dirs = qw(dir1 dir2 dir3);
# Normally via Getopt::Long
my $verbose = 1;

for my $dir (@dirs) {
    # Do some stuff, then:
    processDir( { dir => $dir, script => $script, verbose => $verbose } );

    # which would be exactly the same as:
    processDir( { script = > $script, dir => $dir, verbose => $verbose } );

    # or this:
    processDir( { verbose => $verbose, script => $script, dir => $dir } );

    # or any other combination you can think of.
}

##</code><code>##

sub contains
{
    my $self = shift;
    my %args = @_ == 1 ? ( date => shift ) : @_;

    $args{date} ||= 'today';
    $args{style} ||= $self->{_style};

    croak 'Unknown parameter present' if scalar(keys(%args)) > 2;

    ...
}