>perl -wMstrict -le
"my @elements = qw(stop sign light painter porch store front);
 my ($elem) =
   map qr{ $_ }xms,
   join q{ | },
   @elements
   ;
 my $plural = qr{ e? s }xms;
 my $compound = qr{ \b $elem{2,} (?= $plural? \b) }xms;
 ;;
 my $str = qq{a signpainter wanted the stopsigns in front \n}
         . qq{of all his storefronts` frontporches replaced \n}
         . qq{by stoplights to reduce accidents in front \n}
         . qq{of his stores}
         ;
 print qq{[$str]};
 ;;
 my @compounds = $str =~ m{ $compound }xmsg;
 printf qq{'$_' } for @compounds;
"
[a signpainter wanted the stopsigns in front
of all his storefronts` frontporches replaced
by stoplights to reduce accidents in front
of his stores]
'signpainter' 'stopsign' 'storefront' 'frontporch' 'stoplight'