$s = x'00ffff00ffff';
#       [ffff] this a non word-aligned false hit
#             [ffff] Word-align true hit

##</code><code>##

print "'$1' found at ", pos( $s ) - 4 
    while $s =~ m[(?<=^.{4})*?(....)]g;

'the ' found at  0
'quic' found at  4
'k br' found at  8
'own ' found at  12
'fox ' found at  16
'jump' found at  20
's ov' found at  24
'er t' found at  28
'he l' found at  32
'azy ' found at  36

##</code><code>##

#! perl -slw
use strict;
use bytes;

my $bindata = pack 'N*', 0000 .. 4000;

for my $n ( 16_000_000 .. 17_000_000 ) {
	no warnings;
	
	my $bin = pack 'N', $n;
	
	my $p = -1;
	while( ( $p = index( $bindata, $bin, $p+1 ) ) >= 0 ) {
		if( not $p % 4 ) {
			print "\nindex found $n at $p";
		}
		else{
			print "\nindex found $n at (non % 4 == 0) $p";
		}
	}
	
	if( $bindata =~ m[(?<=^.{4})*?\Q$bin\E]g ) {
		print "regex found $n at ", pos( $bindata ) - length( $bin );
	}
}

__END__
P:\test>test2

index found 16056320 at (non % 4 == 0) 982
regex found 16056320 at 982

index found 16121856 at (non % 4 == 0) 986
regex found 16121856 at 986

index found 16187392 at (non % 4 == 0) 990
regex found 16187392 at 990

index found 16252928 at (non % 4 == 0) 994
regex found 16252928 at 994

index found 16318464 at (non % 4 == 0) 998
regex found 16318464 at 998

index found 16384000 at (non % 4 == 0) 1002
regex found 16384000 at 1002

index found 16449536 at (non % 4 == 0) 1006
regex found 16449536 at 1006

index found 16515072 at (non % 4 == 0) 1010
regex found 16515072 at 1010

index found 16580608 at (non % 4 == 0) 1014
regex found 16580608 at 1014

index found 16646144 at (non % 4 == 0) 1018
regex found 16646144 at 1018

index found 16711680 at (non % 4 == 0) 1022
regex found 16711680 at 1022

index found 16777216 at (non % 4 == 0) 7

index found 16777216 at (non % 4 == 0) 1026
regex found 16777216 at 7

index found 16777217 at (non % 4 == 0) 1031
regex found 16777217 at 1031

index found 16777218 at (non % 4 == 0) 2055
regex found 16777218 at 2055

index found 16777219 at (non % 4 == 0) 3079
regex found 16777219 at 3079

index found 16777220 at (non % 4 == 0) 4103
regex found 16777220 at 4103

index found 16777221 at (non % 4 == 0) 5127
regex found 16777221 at 5127

index found 16777222 at (non % 4 == 0) 6151
regex found 16777222 at 6151

index found 16777223 at (non % 4 == 0) 7175
regex found 16777223 at 7175

index found 16777224 at (non % 4 == 0) 8199
regex found 16777224 at 8199

index found 16777225 at (non % 4 == 0) 9223
regex found 16777225 at 9223

index found 16777226 at (non % 4 == 0) 10247
regex found 16777226 at 10247

index found 16777227 at (non % 4 == 0) 11271
regex found 16777227 at 11271

index found 16777228 at (non % 4 == 0) 12295
regex found 16777228 at 12295

index found 16777229 at (non % 4 == 0) 13319
regex found 16777229 at 13319

index found 16777230 at (non % 4 == 0) 14343
regex found 16777230 at 14343

index found 16777231 at (non % 4 == 0) 15367
regex found 16777231 at 15367

index found 16842752 at (non % 4 == 0) 1030
regex found 16842752 at 1030

index found 16908288 at (non % 4 == 0) 1034
regex found 16908288 at 1034

index found 16973824 at (non % 4 == 0) 1038
regex found 16973824 at 1038