in reply to Bug in script, regex help req extreme urgent

Use a look-behind assertion. Rather than looking for the string 'module ' then testing if the $ARGV[2] string follows, look for the $ARGV[2] string and see if it is preceded by the string 'module '.

my $match = "(?<=module )$ARGV[2]"

Using Look-ahead and Look-behind

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Re^2: Bug in script, regex help req extreme urgent
by sid.verycool (Novice) on Mar 09, 2013 at 13:43 UTC
    tHANKS Don Coyote, actually i tried what i suggested again... and fortunately its doing what i want, but i dont have any idea how its doing its job, specially the substitution part? we say it to replace $string with ARGV1$1. 
    my $match = "(?<=module )$ARGV[2].*?([\\(;])";
print "$match";

my $filename = $ARGV[0];

open (INFILE, "<", $filename)  or  die "Failed to read file $filename 
+: $! \n";

$string =  <INFILE>;
close INFILE;

$string =~ s/$match/$ARGV[1]$1/sg;
print "$1";

    [download]
    The output is just what i want i.e. 
    script.pl f5 NEW OLD
(?<=module )OLD.*?([\(;])
#> cat f5
//Verilog HDL for "tt", "hh" "functional"
// if i write the word module here the script goofs up
`timescale 1ps/10fs


module NEW(Y, A, B );
    output Y;
    input A;
    input B;

endmodule

    [download]
    please help me in understanding this
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      Its solves my issue but fails in the scenario when i have  module this is in between OLD(A, B, Y);, i even want my script to change it to,   module this is in between NEW(A, B, Y); hence i tried doing this  (?<=module .*)$ARGV[2].*?([\\(;])"; which doesnt work and shell says <bold>Variable length lookbehind not implemented in regex; marked by <-- HERE in m/(?<=module .*)NEW.*?(\(;) <-- HERE / at script.pl line 23.</bold>. How can i implement this?
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Re^2: Bug in script, regex help req extreme urgent
by sid.verycool (Novice) on Mar 09, 2013 at 12:57 UTC
    If i do 
    my $match = "(?<=module ).*?$ARGV[2].*?([\\(;])";

    [download]
    Then the output is 
    //Verilog HDL for "tt", "hh" "functional"
// if i write the word module module NEW(Y, A, B );
    output Y;
    input A;
    input B;

endmodule

    [download]
    this does not solve the issue :(
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