my $foo    = ();
my $bar    = \$foo;
my $string = 'hello <--REPLACE-->';

# das klappt natürlich nicht
$string =~ s/<--REPLACE-->/$bar/;

$foo = 'world';
print $string, "\n";

$foo = 'community';
print $string, "\n";

#!/usr/bin/perl

use strict;
use warnings;

package RefReplacer;

use overload '""' => \&replace;

my $self;

sub new{
    my ($class,$string) = @_;
    $self = {};
    bless $self,$class;
    $self->string($string);
    return $self;
}

sub string{
    my ($self,$string) = @_;
    $self->{string} = $string if defined $string;
    return $self->{string};
}

sub pattern{
    my ($self,$pattern,$ref) = @_;
    $self->{pattern}->{$pattern} = $ref;
}

sub replace{
    my $string = $self->string;
    for my $pat(keys %{$self->{pattern}}){
        my $ref = $self->{pattern}->{$pat};
        $string =~ s/$pat/$$ref/g;
    }
    
    return $string;
}

package main;

my $foo    = ();
my $bar    = \$foo;
my $string = RefReplacer->new('hello <--REPLACE-->');
$string->pattern('<--REPLACE-->',\$foo);

# das klappt natürlich nicht

$foo = 'world';
print $string, "\n";

$foo = 'community';
print $string, "\n";

        $string =~ s/\Q$pat\E/$$ref/g;

$string =~ s/$pat/$$ref/g;