You posted a set of "data" that has three lines, and it's hard to know how to interpret that. (How many fields are there, really? Why is it that the groups of hyphens on the second line do not match the widths of fields on the other lines?)

Meanwhile, the script is reading the output from some other process. (Is the data sample the exact output of that process? If not, it would be better to show us that output.)

If the problem is that the first line of output from the other process (the column headings?) has more fields than any of the other lines, why even worry about it? Just skip that line:

open( SANCLI, "datapath query essmap |" ) or die "unable to open pipe.
+.. $!";
$_ = <SANCLI>;  # read first line, do nothing with it
while(<SANCLI>) {
    ...
[download]

If you actually need to keep the column headings (e.g. to use them as hash keys later), just remove the "P" column from that one line before splitting it:

open( SANCLI, "datapath query essmap |" ) or die "unable to open pipe.
+.. $!";
$_ = <SANCLI>;
s/\s+P\s+/ /;
my @col_headings = split;

while(<SANCLI>) {
    my %fields;
    @fields{@col_headings} = split;
    ...
}
[download]

If I'm not answering your question, please try to be more clear about what the problem is.