This code: 
#!/usr/bin/perl
# removenewlines
use warnings;
#use strict;

$/ = undef;
open IN, shift or die "Failed at opening given file: $!";

$InFile = <IN>;
$Output = $InFile;

$Output =~ s/\n/things/g;
print $Output . "\n";

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is behaving oddly, and I'm not sure what the reason is. When it finds a newline character in my CSV file, it not only removes the newline and replaces it with "things", as it should, but it also includes a fair amount of the line of text before it (the amount varies, and it doesn't seem to follow any logic. Sometimes it removes text starting in the middle of a word, sometimes after another character, though in the file I have it's always removing the same amount each time. It seems to only remove less than 100 characters each time (though I've only tested it with a fairly small file).
I know about a few CSV modules, but they aren't serving my needs (ie, they aren't capturing the data correctly 100% of the time), so I'm building what I need as I need it. The main snag has been that one of the CSV files can contain newline characters within a field, so I started making code to replace them. It wasn't working, so I made this to test the behavior... and now I'm stumped.
Below are two of the fields before and after:

An example of a "normal" CSV line (they all have quoted areas): 

"inkjet001","Inkjet Printer",4,"prodimages/inkjetprinter.gif","prodima
+ges/linkjetprinter.gif",95,90,130,4,0,2.02,1,1,0,0,"",,0,0,0,"This in
+kjet printer really packs a punch for the home user. Full color print
+s at photo quality. Perfect for everything from letters to the bank m
+anager, to printing out your favourite digital family pictures.","Thi
+s inkjet printer really packs a punch for the home user. Full color p
+rints at photo quality. Perfect for everything from letters to the ba
+nk manager, to printing out your favourite digital family pictures.<b
+r>As well as a larger image, you can use this ""Long Description"" to
+ add extra detail or information about your products."

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"inkjet001","Inkjet Printer",4,"prodimages/inkjetprinter.gif","prodima
+ges/linkjetprinter.gif",95,90,130,4,0,2.02,1,1,0,0,"",,0,0,0,"This in
+kjet printer really packs a punch for the home user. Full color print
+s at photo quality. Perfect for everything from letters to the bank m
+anager, to printing out your favourite digital family pictures.","Thi
+s inkjet printer really packs a punch for the home user. Full color p
+rints at photo quality. Perfect for everything from letters to the ba
+nk manager, to printing out your favourite digital family pictures.<b
+r>As well as a larger image, you can use this ""Long Descthings

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An example of a "line" with a newline: 

"testproduct","Cheap Test Product",3,"prodimages/computercable.gif","p
+rodimages/lcomputercable.gif",0.01,0.01,0,0,0,3,1,1,0,0,"",,0,0,0,"Th
+is is a cheap product for testing. Note how you can use <b>HTML <font
+ color='#FF0000'>Markup</font></b> in product descriptions.<br>Also n
+ote that as you change the product options, the price changes automat
+ically.","This is a cheap product for testing. Note how you can use <
+b>HTML <font color='#FF0000'>Markup</font></b> in product description
+s.<br>
In the long description you can go into more detail about products."

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"testproduct","Cheap Test Product",3,"prodimages/computercable.gif","p
+rodimages/lcomputercable.gif",0.01,0.01,0,0,0,3,1,1,0,0,"",,0,0,0,"Th
+is is a cheap product for testing. Note how you can use <b>HTML <font
+ color='#FF0000'>Markup</font></b> in product descriptions.<br>Also n
+ote that as you change the product options, the price changes automat
+ically.","This is a cheap product for testing. Note how you can use <
+b>HTML <font color=thingsIn the long description you can go into more
+ detail about products."

[download]

In reply to newline substitution is removing text too by Groxx

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