Here's how I'd do it:

# keyboard sequence (qwertz), for request from germany
my $k = <<EOH;
1234567890ß'
!"§$%&/()=?`
qwertzuiopü+
asdfghjklöä#
<yxcvbnm,.-
>YXCVBNM;:_
EOH

my @k = split/\n/,$k;

# update: strings for diagonal mapping, e.g 1qa 2ws 3ed
# the other diagonal is left as an exercise to the reader
push @k, map { my $i=$_ ;join('',map{substr($k[$_],$_>3? $i+1:$i,1)} 0
+,2..4) } 0..11;
push @k, map { my $i=$_ ;join('',map{substr($k[$_],$_>3? $i+1:$i,1)} 1
+..3,5) } 0..11;

my @matches;
chop (my $seq = <STDIN>);
for my $i(0..length($seq) - 3) {
    my $t = substr($seq,$i,3);
    push @matches, /$t/ig for @k;
}
print "matches: @matches\n";
__END__
djuriops>yxcvatgb5
matches: iop >YX yxc YXC xcv XCV tgb tgB
[download]

--shmem

update: added diagonal match

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}