a = [ 'a','b','c','d','e','f','g' ]
a[:3]    # abc
a[:-3]  # abcd
a[3:]   # defg
a[-3:]  # efg

##</code><code>##

my @a = qw/a b c d e f g/;

# python a[:3] = 'abc' (ie. select first 3)
say join( '', head( 3, @a)) . " should be abc";
# python a[:-3] = 'abcd' (ie. omit last 3)
say join( '', head( -3, @a)) . " should be abcd"; # except when -0!
# python a[3:] = 'defg' (ie. omit first 3)
say join( '', tail( -3, @a)) . " should be defg"; # except when -0!
# python a[-3:] = 'efg' (ie. select last 3)
say join( '', tail( 3, @a)) . " should be efg";