For ...um ... nFor.

#! perl -slw
use strict;

sub nFor(&@) {
    my $code = shift;
    die "First argument must be a code ref" unless ref( $code ) eq 'CO
+DE';
    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 ];
    }
}


our $TMPL //= '{a|b}cd{f|g|h}';

my @as = map {
    /\|/ ? [ split '\|', $_ ] : length() ? [$_] : ();
}  split '\{([^}]+)\}', $TMPL;


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

__END__
[ 1:50:21.76] C:\test>junk43 -TMPL="{a|b}def{g|h}j{K|l}m{n|o}p{q|r}"
adefgjKmnpq
adefgjKmnpr
adefgjKmopq
adefgjKmopr
adefgjlmnpq
adefgjlmnpr
adefgjlmopq
adefgjlmopr
adefhjKmnpq
adefhjKmnpr
adefhjKmopq
adefhjKmopr
adefhjlmnpq
adefhjlmnpr
adefhjlmopq
adefhjlmopr
bdefgjKmnpq
bdefgjKmnpr
bdefgjKmopq
bdefgjKmopr
bdefgjlmnpq
bdefgjlmnpr
bdefgjlmopq
bdefgjlmopr
bdefhjKmnpq
bdefhjKmnpr
bdefhjKmopq
bdefhjKmopr
bdefhjlmnpq
bdefhjlmnpr
bdefhjlmopq
bdefhjlmopr
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