#! perl -slw
use strict;

sub bitFields{
    my( $val, $pat ) = @_;
    my @fields = unpack $pat, reverse unpack 'b32', pack 'L', $val;
    return unpack 'L*', pack '(b32)*', map scalar( reverse), @fields;
}

my( $linkStatus, $cardStatus, $reserved, $intrStatus ) =
    bitFields( 123456789, 'x2 a2 a3 a7 a15' );

print for $linkStatus, $cardStatus, $reserved, $intrStatus;

__END__
C:\test>bitFields.pl
0
3
86
31138

##</code><code>##

sub bitFields{
    unpack 'L*', pack'(b32)*', map scalar( reverse),
        unpack $_[1], reverse unpack 'b32', pack 'L', $_[0];
}