#! perl -slw
use strict;

sub nFor(&@) {
    my $code = shift;
    die "First argument must be a code ref" unless ref( $code ) eq 'CODE';
    my @limits = @_;

    my @indices = ( 0 ) x @limits;

    for( my $i = $#limits; $i >= 0; ) {
        $i = $#limits;
        $code->( @indices ), ++$indices[ $i ]
            while $indices[ $i ] < $limits[ $i ];
        $i = $#limits;
        $indices[ $i ] = 0, ++$indices[ --$i ]
            while $i >= 0 and $indices[ $i ] == $limits[ $i ];
    }
}

my @array = (
    [ "a", "b", "c", ],
    [ "1", "2", "3", "4", ],
    [ "x", "y", ],
);

nFor {
    print join '', map $array[ $_ ][ $_[ $_ ] ], 0 .. $#_
} map scalar @$_, @array;

__END__

c:\test>nfor
a1x
a1y
a2x
a2y
a3x
a3y
a4x
a4y
b1x
b1y
b2x
b2y
b3x
b3y
b4x
b4y
c1x
c1y
c2x
c2y
c3x
c3y
c4x
c4y