The following code uses a regex to extract the various fields to an array:

use strict;
use warnings;

while (<DATA>) {
    chomp;
    next unless length;

    my @items = /
        SS\s+ (\S+)\s+  # SS field
        PL\s+ (.*?)     # PL field - may have trailing white space
        PV    (.*?)     # PV field - includes white space
        C[LT] (.*?)     # CL field - includes white space
        RL    (.*?)     # RL field - includes white space
        SA\s+ (\S+)\s+  # SA field
        DS\s+ (\S+)     # DS field
    /xi;                # Allow comments and white space in regex. Ign
+ore case

    if (@items != 7) {
        # Warn then skip badly formed lines
        warn "Unrecognised line format: $_\n";
        next;
    }

    # Do stuff with the extracted fields
    print '>', join ('<, >', @items), "<\n";
}

__DATA__
SS  21   PL 2#3  PV  51.3 CL #110 +0 RL 126' SA 106 DS 93
SS  21   PL 2#3  PVa51.3 CT^ 110 +0 RL126, SA 106 DS 93
SS  21   PL 2#3  PV   51.3 CL #110 +0 RL 126' SA 106 DS 93
[download]

Prints:

>21<, >2#3  <, >  51.3 <, > #110 +0 <, > 126' <, >106<, >93<
>21<, >2#3  <, >a51.3 <, >^ 110 +0 <, >126, <, >106<, >93<
>21<, >2#3  <, >   51.3 <, > #110 +0 <, > 126' <, >106<, >93<
[download]