c:\@Work\Perl>perl -wMstrict -le
"print $];
 my $s = 'alter string-N-U-M-B-E-R-O-N-E and string-N-U-M-B-E-R-T-W-O.';
 $s =~ s/(?=\S+([[:upper:]]-){2,}[[:upper:]]\b)/%/g;
 print qq{'$s'};
"
5.008009
'alter %s%t%r%i%n%g%-%N%-%U%-%M%-%B%-%E%-%R%-O-N-E and %s%t%r%i%n%g%-%N%-%U%-%M%-%B%-%E%-%R%-T-W-O.'

5.010001
'alter %string-N-U-M-B-E-R-O-N-E and %string-N-U-M-B-E-R-T-W-O.'

5.012003
'alter %string-N-U-M-B-E-R-O-N-E and %string-N-U-M-B-E-R-T-W-O.'

5.014004
'alter %s%t%r%i%n%g%-%N%-%U%-%M%-%B%-%E%-%R%-O-N-E and %s%t%r%i%n%g%-%N%-%U%-%M%-%B%-%E%-%R%-T-W-O.'