in reply to Style or Clarity?

That sort of logical structure can be recast as a case switch, ala perlsyn,

SWITCH: { $tmp eq 'F' and last SWITCH; $tmp =~ /[MICL]/ and do { # Some things... } , last SWITCH; # do default else thing }
At the expense of comprehensibility, you can omit the last clause from a statement to have processing continue.

After Compline,