To pack using bitstrings, you have to have bitstrings (strings of 1s and 0s), not decimal numbers. You can get bitstrings from sprintf: 
my ($pos, $aw, $stru) = (2, 5, 6);
my $bits = sprintf('%06b%05b%03b%02b', 0, $stru, $aw, $pos);
print "Bits=<$bits>\n";
my $bstr=pack('b16', $bits);
printf "<$bstr> is %d bytes\n", length($bstr);
print "\nUnpack: ", unpack('B*', $bstr), "\n";

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If you use format strings like 'b6 b5 b3 b2', each unit will be padded out to full byte width, rather than being all jammed together.
The PerlMonk tr/// Advocate

In reply to Re: using pack() to build a 16 bit word by Roy Johnson
in thread using pack() to build a 16 bit word by shelob101

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