#!/usr/bin/perl -w
use strict;
sub mod_perl {
    {
        my $static1;
        print "[", defined($static1) ? $static1 : "undef", "] ";
        BEGIN { $static1= "Hello" }
        sub sub1 {
            my $old= $static1;
            $static1= shift if @_;
            return $old;
        }
    }
    BEGIN {
        my $static2= "Hi";
        print "<$static2> ";
        sub sub2 {
            my $old= $static2;
            $static2= shift if @_;
            return $old;
        }
    }
    print "(",sub1(shift),") ";
    print "(",sub2(shift),")\n";
}
mod_perl(qw( Goodbye Bye ));
mod_perl(qw( Morning Morn ));
mod_perl(qw( Evening Eve ));
mod_perl();

##</code><code>##

Variable "$static1" will not stay shared at static.pl line 9.
<Hi> [Hello] (Hello) (Hi)
[undef] (Goodbye) (Bye)
[undef] (Morning) (Morn)
[undef] (Evening) (Eve)

##</code><code>##

sub uniqueNonBlanks {
    my( $avItems )= @_;
    my @return;
    for my $item (  @$avItems  ) {
        my %seen= ( "" => 1 ) BEGIN;
        push @return, $item   unless $seen{$item}++;
    }
    return wantarray ? @return : \@return;
}

##</code><code>##

my @a= uniqueNonBlanks("Why","","I","Why");
my @b= uniqueNonBlanks("Why","You","Be","I");
$"= ",";
print "(@a) (@b)\n";

##</code><code>##

sub validateOptions {
    my( $hvOptions, $hvUserOpts )= @_;
    for my $key (  keys %$hvOptions  ) {
        $hvOptions->{$key}= delete $hvUserOpts->{$key}
            if  exists $hvUserOpts->{$key};
    }
    if(  %$hvUserOpts  ) {
        my $subName= (caller(1))[3];
        croak "$subName: Invalid options (",
            join(",",keys %$hvUserOpts),")";
    }
    return $hvOptions;
}


BEGIN {
    my %defaults= ( Access=>READ_ONLY, Delimiter=>"/" );
    sub Open {
        my( $keyName, $hvUserOpts )= @_;
        my $hvOpts= validOptions( {%defaults}, $hvUserOpts );
        # ...
    }
}

BEGIN {
    my %defaults= ( Delimiter=>"/", Translate=>"text" );
    sub Read {
        my( $handle, $hvUserOpts )= @_;
        my $hvOpts= validOptions( {%defaults}, $hvUserOpts );
        # ...
    }
}

##</code><code>##

our %Open_defaults= ( Access=>READ_ONLY, Delimiter=>"/" );
sub Open {
    my( $keyName, $hvUserOpts )= @_;
    my $hvOpts= validOptions( {%Open_defaults}, $hvUserOpts );
    # ...
}

our %Read_defaults= ( Delimiter=>"/", Translate=>"text" );
sub Read {
    my( $handle, $hvUserOpts )= @_;
    my $hvOpts= validOptions( {%Read_defaults}, $hvUserOpts );
    # ...
}

##</code><code>##

sub mod_perl {
    our $static= "Hi";
    sub sub1 {
        my $old= $static1;
        $static1= shift if @_;
        return $old;
    }
    # ...
}

##</code><code>##

sub mod_perl {
    {
        my $static1 BEGIN;
        $static1= "Hi";
        sub sub1 {
            my $old= $static1;
            $static1= shift if @_;
            return $old;
        }
    }
    # ...
}

##</code><code>##

sub mod_perl {
    sub sub1 {
        my $static1= "Hi" STATIC;
        my $old= $static1;
        $static1= shift if @_;
        return $old;
    }
    # ...
}