toolic++ ; By handling the first line separately, you can remove all the special cases that you had embedded in your regex, and thereby make it harder to mis-parse your data. The version below correctly handles whitespace in the second field.

Working, tested code:

#!/usr/bin/env perl
use Modern::Perl;

my $dash_or_digits     = qr{ (?: - | \d+ ) }msx;
my $string_with_spaces = qr{ \w [\s\w]*?   }msx;
my $re = qr{
 \A
    \s* (                  \d+ ) # PID
    \s+ ( $string_with_spaces  ) # POLS
    \s+ (                  \d+ ) # U(%)
    \s+ ( $string_with_spaces  ) # POOL_NAME
    \s+ (                  \d+ ) # Seq#
    \s+ (                  \d+ ) # Num
    \s+ (                  \d+ ) # LDEV#
    \s+ (     $dash_or_digits  ) # H(%)
    \s+ (     $dash_or_digits  ) # VCAP(%)
    \s+ (                  \w+ ) # TYPE
    \s+ (                  \w+ ) # PM
    \s*
 \z
}msx;

my $first_line = <DATA>;
chomp $first_line;
my @field_names = split ' ', $first_line;
say join ';', @field_names;

while ( <DATA> ) {
    chomp;
    my @fields = /$re/ or die;
    warn if scalar(@field_names) != scalar(@fields);
    say join ';', @fields;
}
__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
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Output:

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
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