Update: crazyinsomniac kindly pointed out that this valuable piece of info was left out of my post:

$CGI::revision = '$Id: CGI.pm,v 1.49 2001/02/04 23:08:39 lstein Exp $'
+;
$CGI::VERSION='2.752';
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Below you will find lines 272 - 312 of CGI.pm of which param() is a method. There is a WHOLE lot more documentation on param() in CGI.pm 's pod.
HTH
jg

#### Method: param
# Returns the value(s)of a named parameter.
# If invoked in a list context, returns the
# entire list.  Otherwise returns the first
# member of the list.
# If name is not provided, return a list of all
# the known parameters names available.
# If more than one argument is provided, the
# second and subsequent arguments are used to
# set the value of the parameter.
####
sub param {
    my($self,@p) = self_or_default(@_);
    return $self->all_parameters unless @p;
    my($name,$value,@other);

    # For compatibility between old calling style and use_named_parame
+ters() style, 
    # we have to special case for a single parameter present.
    if (@p > 1) {
    ($name,$value,@other) = rearrange([NAME,[DEFAULT,VALUE,VALUES]],@p
+);
    my(@values);

    if (substr($p[0],0,1) eq '-') {
        @values = defined($value) ? (ref($value) && ref($value) eq 'AR
+RAY' ? @{$value} : $value) : ();
    } else {
        foreach ($value,@other) {
        push(@values,$_) if defined($_);
        }
    }
    # If values is provided, then we set it.
    if (@values) {
        $self->add_parameter($name);
        $self->{$name}=[@values];
    }
    } else {
    $name = $p[0];
    }

    return unless defined($name) && $self->{$name};
    return wantarray ? @{$self->{$name}} : $self->{$name}->[0];
}
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Think a race on a horse on a ball with a fish! TG