I'm digging through the Pragmatic Programmers book and had some 
questions about regex support.

Initially they only mention .sub and .gsub.

If I wanted to write a regex block using additional flags, say something 
like this:
s/perl/ruby/igsm

What that be expressed as:

"my favorite programming language is perl".gsub(/perl/ism, 'ruby')

???
What about the 'x' option?