use Algorithm::Loops qw( NestedLoops );

my @special_chars = qw( : ; , = - );

my $corrupt_qfn = ...;

my $iter = NestedLoops([
   map { $_ eq " " ? \@special_chars : [ $_ ] }
      split( /( )/, $corrupt_qfn, -1 )
]);

while ( my @parts = $iter->() ) {
   my $possible_qfn = join( "", @parts );

   say for $possible_qfn;
}