This is slightly more readable:

sub fix32{ $_[0] & 0xffffffff }

for( my $h = 16; $h < 80; $h++ ) {
    $i[$h] = a2(
        fix32( fix32( fix32( $i[$h - 3] ^ $i[$h - 8] ) ^ $i[$h - 14] )
+ ^ $i[$h - 16] )
        , 1
    );
}
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