Before doing the hard part, I looked at the speeds halfway. It is not worth pursuing.

Indeed. My initial thought for this was to use unpack, and I came up with this unholy construct:

unpack 'vccc', join'',map{ pack'b*', $_ } unpack 'a14a6a6a6', unpack '
+B32', pack 'N', $n;
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Which does the job but (not unexpectedly) is an order of magnitude slower than my second attempt in the OP.

That was a pretty good saving, but whenever I have asked these type of questions in the past, someone has always come up with a better solution.

And indeed, salva has; albeit only a further 20% saving. I also tried using separate lookup tables to save a dereference to no avail:

#! perl -slw
use strict;
use Time::HiRes qw[ time ];

my @lookup; $#lookup = 0x3ffff;
$lookup[ $_ ] = [ ( $_ & 0x3f000 ) >> 12, ( $_ & 0xfc0 ) >> 6, $_ & 0x
+3f ]
    for 0 .. 0x3ffff;

my( @nxt, @mid, @bot );
$nxt[ $_ ] = ( $_ & 0x3f000 ) >> 12,
$mid[ $_ ] = ( $_ & 0xfc0 ) >> 6,
$bot[ $_ ] = $_ & 0x3f
    for 0 .. 0x3ffff;

sub stuff{
#    print "@_";
}

our $ITERS //= 10e6;

my $n = 0x80061861;


my $start = time;
for ( 1 .. $ITERS ) {
    stuff(
        ( $n & 0xffc00000 ) >> 18,
        ( $n & 0x0003f000 ) >> 12,
        ( $n & 0x00000fc0 ) >>  6,
        ( $n & 0x0000003f )
    );
}
printf "Shift&and took: %.12f seconds\n", ( time() - $start ) / $ITERS
+;

$start = time;
for ( 1 .. $ITERS ) {
    stuff( $n >> 18, @{ $lookup[ $n & 0x3ffff ] } );
}
printf "  Lookup  took: %.12f seconds\n", ( time() - $start ) / $ITERS
+;

$start = time;
for ( 1 .. $ITERS ) {
    my $i = $n & 0x3ffff;
    stuff( $n >> 18, $nxt[ $i ], $mid[ $i ], $bot[ $i ] );
}
printf "  Lookup2 took: %.12f seconds\n", ( time() - $start ) / $ITERS
+;

$start = time;
for ( 1 .. $ITERS ) {
    stuff( unpack 'vccc', join'',map{ pack'b*', $_ } unpack 'a14a6a6a6
+', unpack 'B32', pack 'N', $n );
}
printf "(un)pack  took: %.12f seconds\n", ( time() - $start ) / $ITERS
+;

__END__
C:\test>1021064
Shift&and took: 0.000000482421 seconds
  Lookup  took: 0.000000386419 seconds
  Lookup2 took: 0.000000547556 seconds
(un)pack  took: 0.000005933478 seconds

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