in reply to How do I match a expression start with $a and not contain $b after $a

This isn't an answer to your question, it's just a warning about better not using $a and $b except with sort because it can cause some funny problems:
#!/opt/gnu/bin/perl -w use strict; $a = 40; # error because of use strict? no $b = $a; # error again ? no
This code will not fail although neiter $a nor $b is declared despite of use strict.

Best regards,
perl -e "$_=*F=>y~\*martinF~stronat~=>s~[^\w]~~g=>chop,print"