Don't use $&! It slows down all the regexp in your program (including modules) that don't have captures. Use captures instead. 
while ($string =~ /([CSH][CSHL]*[CSH])/g) {
    print "$1, ";
}

[download]

Use join to avoid the trailing comma. 

print join ', ', $string =~ /([CSH][CSHL]*[CSH])/g;

[download]

An alternative approach would be to strip out the offending L characters. 

for ($string) {
   s/-L+|L+-/-/g;
   s/^L+//;
   s/L+$//;
   print join ', ', /([CSHL]{2,})/g;
}

[download]

Update: Added s/^L// and s/L$//.
Update: Changed L to L+.
Update: Accidently changed too many things to "+"s. Fixed.

In reply to Re: Regexp: How to match in middle but not the ends? by ikegami
in thread Regexp: How to match in middle but not the ends? by cormanaz

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