I figured out a way to drop the 8-char binary string to a 5-char binary string and simplify some of the math. Unfortunately, the simpler math uses + instead of | so the precedence is wrong so I'd need two sets of parens, which makes the math expression 2 characters longer (despite the calculation being simpler). That would still be an over-all net reduction by one character. But that involves recomputing all of the bits, so I'm not including that trick.

But some standard golfing on the rest did get me down to 177 (updated from 179) chars:

#!/usr/bin/perl
open SEG, ">segment.pl" or die "Can't write seg.pl: $!\n";
binmode SEG;
while(<DATA>){
s/::::::::/pack"H*",'1f10001100100111'/e;
s/!!!!!!!!!!!!!!!/pack"H*",'fca88a04228f12420caacc30125084'/e;
print SEG $_;
}
__END__
#!/usr/bin/perl

sub d{
y/01/ #/for@p=unpack"b5"x8,"::::::::";@s=grep$_,split/(..)/,
unpack"b*",'!!!!!!!!!!!!!!!';map{$l=$_;join($",map{y/-./ab/;
$p[4&$l*4|3&$s[$l+5*hex]]}split//,$_[0]).$/}0,1,1,2,3,3,4
}

print d("123-45");
print d("67.890");
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