How do you build a regexp that matches up to but not including a regular expression in perl? For instance, I have the following plain text file: 
.subckt cct0 v0 v1 v2 v3

+ v4 v5 v6

* useless comment
+ v7 v8 v9
+ va vb

x00 v0 v1 x0 cct1
.ends

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I want to do an operation on everything between the .subckt line up to, but not including the x00 line. so I write something like this: 
while(<>) {
  if(/^\.subckt/../^\w/) {
    print;
  }
}

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This almost works, but it prints out the x00 line. I know that a word transition is what I want to switch on, but I don't know how to capture everything up to, but not including the word transition. On the word transistions I'll need to do another operation.

In reply to regexp match up to but not incliuding... by substrate

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