If all the words are correctly spelt and are in your dictionary, then this appears to make a good attempt at many inputs:

#! perl -slw
use strict;

my @w = do{ local @ARGV = 'words.txt'; <> };
chomp @w;

my $s = 'couldsomeonerecommendaworkingperlmoduletosplitconcatenatedwor
+ds';

my @subset = grep{ $s =~ /$_/ } 'a', 'perl', @w;

my $re1 = join '|', sort{ length( $b ) <=> length( $a ) }@subset;
my $re2 = "($re1)?" x 11;

print for grep defined(), $s =~ /^$re2$/;

__END__
C:\test>junk
could
someone
recommend
a
working
perl
module
to
split
concatenated
words
[download]

But note: I had to add 'a' & 'perl' which don't appear in my dictionary; and I cheated by hardwiring the number of words (11) to look for.

If I change that to a larger number (say 100), then the results are less good:

C:\test>junk
could
someone
recommend
aw
or
king
perl
module
to
split
concatenated
words
[download]

However, if I removed the iffy non-word 'aw' from my rather permissive dictionary, it once again produces the right output, but that just goes to prove how sensitive and dependent the results would be on a good dictionary and correct spelling.