Another solution (though not so elegant as NetWallah's):

$_ = '   ----------  -------------------------  --------  ----  ------
+-------------------  -----  ----  -----------  -----------';
my $i;
print $i += length $_, $/ for split /(?<=-)(?=\s+|$)/;

__END__
__OUTPUT__
13
40
50
56
83
90
96
109
122
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