thanks for the explanation!
I solved my little problem by just opening the handle two times: one for read and one for write access: 
#!perl -w

use strict;
my $line;
my @array;
my $CTLfile = 'y:\perl\test.ctl';
open (CTLHANDLE, "<$CTLfile");
@array = <CTLHANDLE>;
close(CTLHANDLE);
open (CTLHANDLE, ">$CTLfile");
foreach $line(@array){
    $line =~ s/SOURCEREPOSITORYNAME/SOURCEREPOSITORYNAME=Development/g
+;
    print CTLHANDLE "$line";
}
close(CTLHANDLE);

[download]
this seems to work fine.

In reply to Re^2: In place editing of text files by jevaly
in thread In place editing of text files by jevaly

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