I see that you fixed one "unreachable code" problem...
Op should be aware of this in his code:
To be inside of the while (<MAPPINGFILE2>) { loop means that you are not at the eof yet. When this while loop finishes, MAPPINGFILE2 will be eof, but not before.

UPDATE: I decided that this is not right. The read of the very last line will consume all characters and hence reach eof. So you can reach eof before a read of <MAPPINGFILE2> would return an undef (the normal way to detect eof). 

              while (<MAPPINGFILE2>) {

                    chomp();
                    # Skip blank lines and comments
                    next if /^(\s*(#.*)?)?$/;

                    # Split mapping columns (tab)
                    @mapping = split /\t/, $_;

                    # Mapping is matching
                    if ($line =~ m/$mapping[0]/) {

                        $line =~ s/$mapping[0]/$mapping[4]/;
                        @source = split /\t/, $line;
                        $line =~ s/$source[2]/$mapping[2]\tALLOC_$sour
+ce[2]/;
                        push @lines2, $line;
                        last;
                    } elsif (eof(MAPPINGFILE2)) { #correction: ###### 
+Can happen 
                        push @rejects, "Lignes non mappées (Account): 
+"."\t".$line;
                    }
                }

[download]

In reply to Re^2: Optimization tips by Marshall
in thread Optimization tips by sroux

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.