#! /usr/bin/perl 

use strict;

my $s = 'aw --> Re   ';
my $subject = 'AW: Das AW ist AW nun AW mal AW eine AW Antwort :-)';

$s =~ /([^ ]*) *--> *([^ ]*)/;

print "1: \'$1\'\n";
print "2: \'$2\'\n";

print "$subject\n";

$subject =~ s/$1/$2/i;

print "$subject\n";