Nulls (\0, ASCII character 0) are commonly represented by the sequence ^@ by many *NIX tools. While it's unlikely you've set $/ so that chomp would get it chop certainly would if it was the last character of the string. 

$ perl -le '$x = qq{abc\0}; print $x; chop $x; print $x;' | od -xa
0000000      6261    0063    610a    6362    000a                     
+   
           a   b   c nul  nl   a   b   c  nl

[download]

Of course were there more context or (even better) actual code shown someone might be able to make more than that kind of vague guess. (See How (Not) To Ask A Question)

Update: Added sample.

The cake is a lie.
The cake is a lie.
The cake is a lie.

In reply to Re: variable ending with ^@ by Fletch
in thread variable ending with ^@ by himanshu.padmanabhi

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.