A very handy skill in learning Perl is gaining familiarity with documentation. I personally use the Perl documentation hosted on http://perl.org with associated hook-up to my browser search box to keep it immediately on hand. There's also the perldoc command-line utility, ActiveState bundles html-ified docs with its version, and I'm sure a plethora of other options.

For operators, there's perlop. Within that document, the => operator is documented under Comma Operator. It is identical to a comma, except to transforms a bareword left-hand argument to a string. Specifically,

The => operator is a synonym for the comma except that it causes its left operand to be interpreted as a string if it begins with a letter or underscore and is composed only of letters, digits and underscores.

Thus it allows:

my %passwords = ("Matt"   , "s1k1d52",
                 "scuzzy" , "2ab928",
                 "Marky"  , "s8291s",
                 "Jeb"    , "jeb23",
                 );
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to be written as

my %passwords = (Matt   => "s1k1d52",
                 scuzzy => "2ab928",
                 Marky  => "s8291s",
                 Jeb    => "jeb23",
                 );
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which I find to be more intuitive.

The each function has a bit of magic in it. When called with a hash, it will set an iterator in the hash and returns a key, value pair. Each subsequent call (assuming you don't use another function that sets an iterator) returns another key/value pair until they are exhausted, at which time it will return and empty list or undef depending on context. Thus, a while(each) will systematically traverse a hash. On each iteration, I use list assignment to store the key/value pair and then output them in an interpolated string. The examples in each are likely more clear than any explanation I can give.