use strict;

my @bits = (
   "0001",        
   "0010",        
   "0011",              
   "0100",        
   "0101"
);

my @out_data;
my $idx;

foreach my $bitval ( @bits ) {
   $out_data[ $idx++ ] = pack( "b4", $bitval );
}

open( OUT, ">d:\\tmp\\hex_out.txt" );

select( OUT );

print @out_data;

close( OUT );