do{
        ## do something that may or may not change $condition
    } until( $condition )

##</code><code>##

    ## print "foo" until $count becomes 5
    my $count = 0;
    do{
        print "foo\n";
        $count++;
    } until ( $count ==  5 );

    ## call some command until its exit status
    ## is 0 ( success )
    do {
        system( "cmd" );
    } until( $? == 0 );