http://www.perlmonks.org?node_id=854222


in reply to Reading Reg Exp

There are many resources on this in the tutorials-section.

Another resource I find helpful is this online analyzer. It gives you at least a hint where to search for - e.g. in your second example it shows that the ?= is a ZeroWidthPositiveLookahead. Google it to gain deeper knowledge ;-)

HTH, Rata