use strict;
use warnings;

my %seen = ();
print
   grep { ! $seen{$_} ++ }
   grep { m{^s|foo|e f$} }
   <DATA>

__END__
s
erartt
e p
s
foo
e f
s
adflkja

##</code><code>##

s
foo
e f

##</code><code>##

my $lines = '';
{
    local $/;
    $lines = <DATA>;
}