Regular Expression Mastery

Another Disaster

/^(\w+|::)*$/

Matches Perl identifiers like Foo and Getopt::Std.
What does it do with abcd! ?

        \w+             <a  b  c  d> !      No good
        \w+ \w+         <a  b  c><d> !      Also no good
        \w+ \w+         <a  b><c  d> !      Also no good
        \w+ \w+ \w+     <a  b><c><d> !      Still no good
        \w+ \w+         <a><b  c  d> !      Also no good
        \w+ \w+ \w+     <a><b  c><d> !      Still no good
        \w+ \w+ \w+     <a><b><c  d> !      Still no good
        \w+ \w+ \w+ \w+ <a><b><c><d> !      Guess what?
        Gives up.

This doesn't include all the times it tried to match :: against one of the letters, or the times it tried making * match no times, or...