perl -le'
    $_ = "..."; 
    s/[\.-]+//g;
    if (/(\S)(\S)(\S)(\S)$/) {
        print "$1$2$3$4"
    }
'

##</code><code>##

perl -le'
    $_ = "..."; 
    s/[\.-]+//g;
    print substr $_, -4;
'