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From: dboles@ccwf.cc.utexas.edu (David Boles)
Newsgroups: comp.lang.perl
Subject: pattern matching question
Message-ID: <49420@ut-emx.uucp>
Date: 23 May 91 18:58:44 GMT
References: <1991May22.193037.12166@cherokee.uswest.com> <1991May22.221507.12660@cherokee.uswest.com>
Sender: news@ut-emx.uucp
Reply-To: dboles@ccwf.cc.utexas.edu (David Boles)
Organization: The University of Texas at Austin
Lines: 54

Warning: PERL NOVICE approaching !!!

I am trying to do the following file manipulation:

p220 p220   20    5
p220 p235   20    7
etc.

 ==>

p220 -20 -5
p220 20 5
p220 -20 -7
p235 20 7
etc.

I am using:

while (<>) {
    s/(p\d*) (p\d*) (\d*) (\d*)/$1 -$3 -$4\n$2 $3 $4\n/;
    print;
}

and I get:

p220 - -
p220 20 5
p220 - -
p235 20 7
etc.

If I take away the minus signs in the replacement string, I just get:

p220
p220 20 5
p220
p235 20 7
etc.

Why aren't $3 and $4 "alive" in the first half of the replacement
string?  What am I missing?

Thanks!

  David Boles



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David Boles                                       Applied Research Laboratories
dboles@ccwf.cc.utexas.edu                       
apas611@chpc.utexas.edu                      This space for rent, apply within.
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