Sure - sorry for being too cryptic. Sometimes it's hard to tell how much detail is needed. :-)

Insert a new line as follows (code snippet taken from your OP):

while (<>) {
    next if m/^\s+$/; # <-- add this line
    my @cellen = ( split /,/, )[ 3, 4 ];
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The regex is anchored to the start (^) and end ($) of the string, and the pattern consists of one or more white space characters (\s+). See perlre and Pattern Matching, Regular Expressions, and Parsing (in the Tutorials section) for more information.

Incidently, the code I added is a bit shorter than it could be, since it utilizes $_. A more verbose version could be:

next if $_ =~ m/^\s+$/;
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or, if you wanted to explicitly assign the input text to a variable before processing, you could do something like this:

while ( my $line = <>) {
    next if $line =~ m/^\s+$/; # <-- add this line
    my @cellen = ( split( /,/, $line ) )[ 3, 4 ];
[download]

HTH