Example: 

01 #!/usr/bin/perl
02
03 use strict;
04 use warnings;
05
06 my $testval;
07
08 my $newval = "$testval test";
09
10 exit;
11
12 __END__

C:\Steve\Dev\PerlMonks\P-2013-10-15@0712-Uninitalized>uninit.pl
Use of uninitialized value $testval in concatenation (.) or string at 
C:\Steve\Dev\PerlMonks\P-2013-10-15@0712\Uninitalized\uninit.pl line 8
.

[download]

Line 8 attempts to build a string using embedded translation of $testval which is, at that time, uninitialized.

So the error message should tell you where to look. All the usual caveats apply; depending on what you're doing, the actual error in Perl could be not exactly on the line where perl caught the error, but at least you have reduced it from a haystack to a handful of hay.

Good luck!

In reply to Re: trap run time errors by marinersk
in thread trap run time errors by kp2a

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.