use warnings;
use strict;

while (<DATA>) {
    chomp;
    my @cols = split;
    my @a1 = splice @cols, 0, 3;
    my @a2 = splice @cols, -7, 7;
    my $pool = join ' ', @cols;
    print join(';', @a1, $pool, @a2), "\n";
}

__DATA__
PID  POLS U(%) POOL_NAME    Seq# Num LDEV# H(%) VCAP(%) TYPE PM
003  POLN   0  Bad name with spaces   13453   2 61443  80   -  OPEN N 
002  POLN  52  DemoSolutions   54068  7 61454  80   -  OPEN N